New Super Mario Bros. is a platform game released in 2006 for the Nintendo DS and the first game in the New Super Mario Bros. series, deliberately modeled after the side-scrolling games in Nintendo's Super Mario Bros. series, but featuring polygonal renderings of some characters and objects to give it a 2.5D look. It's also the first original side-scroller in the series since 1995's Super Mario World 2: Yoshi's Island, and the first to star Mario as the playable character since 1992's Super Mario Land 2 - 6 Golden Coins.

The plot, as usual in 2D Mario games, is rather simple, though with a little interesting twist this time. After his introduction in Super Mario Sunshine, Bowser Jr. (i.e. not his father) marks his debut in 2D Mario by kidnapping Princess Peach, and Mario has to give chase through eight worlds, each with at least one fortress and one castle to rescue her. Each fortress ends with a battle with Jr., who retreats to either another fortress or a castle when defeated; meanwhile, the castles end with a unique boss fight. Before Mario can rescue Peach at the end of each world, Bowser Jr. nabs her and runs off to the next, which is gonna happen a few more times, finally culminating in a team-up fight against Jr. and his father.

The game was Mario's—and the video game industry in general's—grand return to 2D games and revived the 2D side-scrolling game scene single-handedly, receiving critical acclaim upon release and ending up as the best selling Nintendo DS game with over 30 million units sold. The game preserves the classic 2D Mario gameplay but differentiates itself from its predecessors by bringing gameplay elements introduced in 3D Mario games to 2D Mario games alongside introducing various new power-ups, locations, obstacles, enemies and bosses to the franchise. As longtime Mario developer Takashi Tezuka puts it, "You can think of it as carefully preserving the core gameplay while dressing it up with new elements that enhance it."

The Wall Jump, Triple Jump, and Ground Pound make their first appearance in a 2D Mario game here since being introduced to 3D Mario games in Super Mario 64. In addition to the series' usual power ups of the Super Mushroom, Fire Flower, and Starman, NSMB introduced some new ones. The Mega Mushroom turns Mario into a giant à la Super Mario 64 DS, allowing for some massive property damage. The Mini Mushroom shrinks Mario to the size of a mouse, enabling him to get through very small passageways, have a floatier jump, and run on water at the expense of death in one hit. The Blue Koopa Shell allows Mario to protect himself while crouching; when running, he can knock enemies away just like the Koopa shells he kicks. Finally, Shell Mario can swim better underwater.

This game provides examples of:

• Advertised Extra: Downplayed Non-character example. The Mega Mushroom was prominently featured in advertising and marketing material for the game, but it only appears inside a ? Block in a total of four levels. However, Mega Mushroom Toad Houses, Red Flying ? Blocks, and Hammer Bros. providing them can be found in every world, and can be used in any level via the item storage as long as the current area is not too narrow.
• All Deserts Have Cacti: The background and overworld map of the desert themed World 2 feature Egyptian style pyramids. However, World 2-1 features Pokeys, which are sentient cacti, and the boss of World 2 is Mummipokey, who's essentially a mummified cactus.
• Andean Music: The World 6 Map theme is inspired by Andean music.
• Artificial Brilliance: Bowser Jr. in later worlds does something that no other boss with the same weakness in 2D Mario games does, when he sees that Mario is about to Goomba Stomp him he retreats into his spiny shell so he takes damage instead. This little showcase of the computer being a genius is unique to this game and neither Jr. nor other bosses like the Koopalings have done this either before or since.
• Art Evolution: The current design of the Mushroom power-ups is introduced in this game as they previously had various other designs beforehand.
• Attack of the 50-Foot Whatever: Mario can grow bigger than a freaking castle using the Mega Mushroom. The boss of the World 4 castle, Mega Goomba, is a giant Goomba the same size as Mega Mario. Bowser also grows to the same size for the final battle.
• Avenging the Villain: Bowser is dealt with in the very first world, making Bowser Jr. the main antagonist for the rest of the game.
• Awesome, but Impractical: Grabbing a Mega Mushroom from a Mega Mushroom house lets the player keep it in the item reserve to use it in any level. However, there's a difference between being able to use it in any level and being able to use it effectively - most levels are designed with regular-sized Mario in mind, and 9 times out of 10 the player is going to run into a tunnel or right gap that Mega Mario can't fit into and will have to simply wait for the powerup to wear off before they can go any further.
• Back from the Dead: Bowser is dropped into a pool of lava in the game's first world and reduced to a skeleton. He only recovers in World 8, when Bowser Jr. throws his skeleton into a cauldron to bring him back to life.
• Bad with the Bone: Instead of throwing hammers, Dry Bowser throws bones at Mario or Luigi during battle.
• Battle Discretion Shot: In the opening cutscene, Mario takes a short beating from Bowser Jr. offscreen. If you waited long enough on the title screen, a modified version of the cutscene shows that Mario was hit by a Koopa shell, and sometimes Luigi is dragged into the mix.
• Big Boo's Haunt: The Ghost Houses are labyrinthine areas filled with Boo enemies.
• Breaking the Fourth Wall: Closing the DS without turning the game off will result in Mario saying "Ba-bye." Opening it back up will cause Mario to greet you with "It's-a me, Mario!"
• Build Like an Egyptian: The second world is themed heavily after the Egyptian desert, and prominently features pyramids and ancient Egyptian structures throughout.
• Bookends: World 1 has the very first of many bouts against Bowser Jr. in its tower level, and the fight against Bowser in its castle level. The Final Battle in World 8's Bowser's Castle has Mario fighting both of them (albeit together in their stronger forms) one last time.
• Call-Back:
  • Bowser Jr. fight exactly like Boom-Boom (being the boss of the Fortress/Tower levels), especially in his World 1 Tower bout where he simply runs around, hides in his shell when stomped, and the arena is a simply enclosed space with no hazards. And in later bouts, he also jumps (much like Boom-Boom himself) and Took a Level in Badass with newer attacks in later levels (Boom-Boom sprouting a pair of wings, Bowser Jr. fighting much tougher by hiding in his shell more frequently and only being defeated via Fire Flower, Mega Mushroom, and/or a Koopa Shell thrown at him and Shell Mario stunning him).
  • The first Bowser battle in the World 1 Castle is one to Super Mario Bros. 1 first Fake Bowser fight in the World 1 Castle where he mainly spits fire, and there is a moving platform that helps Mario jump over him and hits the switch.
• The Chase: The entire plot of the game revolves around Mario pursuing Bowser Jr. to rescue Peach from his grasp. Go to a world, fight Bowser Jr., watch as he escapes and drags Peach to another world, rinse and repeat until World 8.
• Cheat Code:
  • Beating the game reveals a minor one: selecting a file while holding down the L and R buttons allows the player to play as Luigi. However, beating the game is not required to use this code, and it can be performed at the start of a brand new save file as well as on an already-completed one; there's even a version of the opening cutscene with Luigi instead of Mario (though the credits still show images of Mario regardless of which brother you beat the game as).
  • A more obscure one that the game doesn't give away requires the player to press L, R, L, R, X, Y, X, Y in that order while paused on the map screen; doing so unlocks Challenge Mode, which simply replicates the Ratchet Scrolling of the original Super Mario Bros. 1.
    Message upon activating Challenge Mode: Welcome to the secret Challenge mode. Think you can reach the goal? If you get stuck, press START and choose Return to Map.
• Checkpoint Starvation: 2-6, 3-Tower, 5-Tower, 7-3, 8-5, and the Ghost houses do not have any checkpoints.
• Color-Coded Multiplayer: The minigame mode assigns each player with a color and one protagonist from Super Mario 64 DS. The player order is red (Mario), green (Luigi), yellow (Wario), and blue (Yoshi).
• Creative Closing Credits: The ending credits feature a montage of every single level that had been played in the game. If you play a level that you hadn't before beating the game, it will be added to the credits the next time you see them. The player can also use the stylus to tap the letters in the names that appear in the credits; each letter plays a different sound effect.
• Credits Montage: The top screen shows all the levels you've cleared (even the cannons that you used). In the cases of the towers and castles, it will show the level itself first before the boss, while the final castle shows the level, the boss, and the princess being rescued.
• Creepy Crows: The Crowbers make their debut in this game, appearing in the first level of World 8 and dive bomb Mario/Luigi.
• Cumulonemesis: Unlike the standard Lakitu, whose sentient cloud is merely transporting him airborne, the King Mook Lakithunder sports a darker, more menacing cloud which, during battle, can shoot up to three lightning bolts onto Mario and Luigi as part of its master's Retaliation Mode.
• Damsel in Distress: Bowser Jr. grabs Princess Peach while Mario is distracted by the lightning that strikes her castle, and the rest of the game sees Mario chase Jr. through several worlds in order to save her.
• Deader than Dead: Subverted. Technically already-dead Dry Bowser is nevertheless beaten a second time... but, given his Joker Immunity, still comes back as Bowser for the Final Battle.
• Death Mountain: World 6, in which Mario has to venture through gray-colored spiral mountains. Some of the levels bring back elements from other worlds (namely desert, lake, jungle and ice), making it also an example of Hailfire Peaks. The spiral mountains return in World 8.
• Dem Bones: Dry Bones reappear in this game and fight the same way as in previous appearances, though they can also be defeated by Mega Mario/Luigi and Shell Mario/Luigi. This game also introduces Super Dry Bones (renamed to Big Dry Bones then Mega Dry Bones in later appearances), which require a ground pound instead of a regular jump to temporarily defeat; as well as Dry Bowser, a skeletal version of Bowser acting as this game's Disc-One Final Boss.
• Demoted to Extra: Some of Yoshi's and Wario's minigames from Super Mario 64 DS reappear, but the characters themselves don't appear at all in the main game.
• Developer's Foresight:
  • If the player uses the Mega Mushroom in the first level to destroy only part of the staircase to the flagpole, a series of Hidden Blocks will appear where the staircase's steps used to be to avoid a softlock.
  • If Mario tries to use the Mega Mushroom in an area where there's not enough space to fully grow, Mario will shrink back to normal size, and the Mega Mushroom will be added to the bottom screen so the player can use it later.
  • For the most part, the developers fully expected players to try playing the game front to back as Luigi after learning the code to use him: every cutscene in the game has a variant with Luigi instead of Mario, Luigi has unique lines and voice clips provided by Charles Martinet, and most assets that are themed after Mario change to reflect Luigi's presence (such as the "Mario Clear" banner being changed to say "Luigi Clear" and being green instead of red, Mario's icons and iris-out silhouettes being replaced with ones of Luigi, etc). The only places that were really overlooked were the credits sequence and wallpapers, which still use imagery and iconography of Mario regardless of which brother the player is using.
  • Normally, once you beat a Tower or a Castle in a World and the scene changes back to the world map, Bowser Jr. will exit the place and drags Peach with him to either that World's Castle or the next World respectively. However, if you skipped to a later World through a Warp Cannon and return back to the Worlds prior to that, then the animation for beating them changes to simply having a white flag being generated from the top of the Tower/Castle, with Bowser Jr. nowhere to be seen in the world map as he's already in the furthest Tower/Castle available to the player.
  • Petey Piranha's encounter begins with him being forcefully awakened by Bowser Jr., who jumped on him to initiate the boss fight. If you fought Petey again or if you only fought Petey after you sent Bowser Jr. to a Tower/Castle that's located in Worlds 6, 7 or 8, then he'll wake up on his own instead. Petey's castle is also the only castle level in the game that has a Star powerup, and the developers accounted for the player grabbing it and making it to Petey before the Star runs out; it defeats him in one hit.
• Digital Tabletop Game Adaptation: The "Table" category of minigames features digital versions of card and board games like Blackjack (Luigi-Jack), Texas Hold-'em (Luigi's Thrilling Cards), and Reversi (Bob-Omb Reverse). Some of them were carried over from Super Mario 64 DS, and some were new additions.
• Disc-One Final Boss: Dry Bowser is the boss of World 8... or rather, the boss of the first half of World 8. After defeating him, the second half opens up, containing volcano themed levels, a second tower and a giant green castle that's the real final level.
• Dual Boss: The final boss is Bowser Jr. and an enlarged Bowser.
• Early-Installment Weirdness: The game has many differences compared to its follow-ups that make it feel so different and unique.
  • This game uses the engine and a number of assets from Super Mario 64 DS two years prior, further showcasing the game's goal of introducing gameplay elements introduced in 3D Mario in the interim to 2D Mario and making it feel more closely connected to that game than to any of its successors. The game introduces the Triple Jump, Wall Jump and Ground Pound from Mario's movement in said game and pre-release footage of this game shows that the punching action was also initially going to be added as well before being ultimately cut, the models for Mario, Luigi, Peach, and Bowser are all taken from 64 DS with certain alterations, the minigame mode returns with nearly every minigame from 64 DS either intact or remade in this game's artstyle along with brand new additions, and the game reuses the "Buh bye!" and "It's-a me, Mario!" voice clips when closing and opening the DS while the game is running.
  • This is the only game in the New subseries to not have the Koopalings as the main bosses, but unique opponents like Mega Goomba, Mummy Pokey, Petey Piranha, and Monty Tank. Bowser also appears as early as the end of World 1 and is Stripped to the Bone then and there, becoming Dry Bowser who later reappears as the penultimate boss. In the other games, he doesn't appear until the final boss battle, and in this game he doesn't have a second phase where he turns into a giant, with the Final Boss instead being a Dual Boss against him and the most advanced version of Bowser Jr.
  • Bowser Jr. appears as every tower's boss, and also lacks his Koopa Clown Car, initially acting like Boom Boom from Super Mario Bros. 3 but in later worlds doing something that no other boss with the same weakness in Mario games does, when he sees that Mario is about to Goomba Stomp him he retreats into his spiny shell so he takes damage instead. This piece of Artificial Brilliance is also unique to this game and neither Jr. nor the Koopalings have done this either before or since.
  • The invincibility theme. It's just the wing cap theme from Super Mario 64 with added percussion, in contrast to later games that use an original version of the invincibility theme featuring only the base melody, without the countermelody heard in 64 (which itself originated in Super Mario World 2: Yoshi's Island).
  • Ground pounding bosses would do double damage to them in this game. Later games would have ground pounds do normal damage to bosses to prevent cheesing. Also, ground pounding a Koopa Troopa or other shelled enemy will not instantly defeat them, but instead immediately sends them sliding.
  • This is also the only game which has a new powerup that hasn't reappeared in any of its sequels in the Blue Shell.
  • This is the only game in the sub-series where there is no second-tier power-up that specializes in flying or gliding. There are also no POW Blocks.
  • Speaking of powerups, collecting eight red coins will only give you a Super Mushroom if you're small. In later entries they always give you the level's second-tier powerup irrespective of form.
  • Unlike later NSMB games, Bowser was voiced via audio taken from sound libraries; the earliest use of it was from the 1957 film The Land Unknown. This was actually the standard for Bowser since Super Mario 64 ten years prior, and all of Bowser's voice clips in this game were ones previously used throughout the N64 era. Following this game, Bowser's voice would instead be provided by a variety of in-house voice actors, each of whom would give Bowser a more human-like voice a-la his portrayal in Super Mario Sunshine, rather than the more overtly animal-like roars. Additionally, the "power-up loss" and "coin" sounds are reused from Super Mario Bros. 1 rather than Super Mario World.
  • The first game also uses a completely different soundtrack from the one that debuted in the Wii game and was reused to varying degrees in the 3DS and Wii U entries. Despite the Koopalings' absence in the first game, a remix of their boss fight from Super Mario Bros. 3 is used for the end bosses, whereas the Wii and Wii U games use another remix of the SMB3 fight for the mid-bosses instead. The 3DS game, meanwhile, features a remix of the Koopaling fight from Super Mario World for its mid-bosses.
  • The game lacks a post-finale Special World, instead opting for bonus lettered levels within the existing worlds that can be unlocked pre-finale (although NSMB2 has both the lettered levels and bonus worlds but with only 6 main worlds). In fact, Worlds 4 and 7 are completely optional, only being accessible as a reward for challenging the World's boss in something akin to a Hard Mode by using Mini Mario; the former by beating the World 2 boss as Mini Mario, and the latter by either beating the World 5 boss as Mini Mario or using the Warp Cannon in World 4.
  • The game has various unlockable wallpapers for the touch screen map, compared to 2's having only one.
  • Unlike the later three games, there is no multiplayer for the main campaign. Instead, the only multiplayer is for the "Mario vs. Luigi" mode (and the separate bonus minigames), which uses exclusive courses. There are also bonus minigames instead of alternate game modes.
  • Blue and Yellow Toad are not playable in this game, only Mario and Luigi (and the latter brother is locked behind a Classic Cheat Code).
  • Compared to the later games, the levels that feature warp cannons show elements of the World you're about to warp to (World 1's and 2's Warp Cannons having a snowy mountain background from World 5, World 3 having World 6's mountain background, World 4 having the Sky background commonly seen in World 7, and World 5 having World 8's ominous background)
  • There is no quicksave feature, so you'll have to replay a tower/castle level or spend Star Coins on a sign if you want to save before you beat the game, which unlocks the ability to save any time. Otherwise, you'll have to take advantage of Sleep Mode (or save states) to avoid losing progress.
  • The game has various unique obstacles and enemies not present in its sequels, of particular note regarding the obstacles, this is the only NSMB game with Spin Blocks that launch Mario/Luigi high into the air to then be able to descend with a drill spin jump, Dorrie as a vehicle, a Giant Wiggler that works as the floor in Sky levels, a Mega Unagi that chases you in underwater levels, and a level switch that turns the entire level upside-down in the final castle level.
  • This is the only game in the NSMB series to have two separate castles in a single world each with their own boss (the regular castle having Dry Bowser, Bowser's Castle having the Final Battle between Bowser and Bowser Jr.). While New Super Mario Bros. U technically has two Castle levels, it's all within the corrupted Peach's Castle, and the first half doesn't even have a boss.
  • The normal final world also is different here compared to its follow-ups, with Bowser's domain entire first half being a Haunted landscape world with enemies such as Crows and Pumpkins and half a Volcano world instead of purely a Lethal Lava Land one like in the sequels.
  • Upon completing a level or boss fight, Mario says "That's a-so nice!" rather than "Oh, yeah! Mario time!", "Hoo hoo! This way!", or "Mario's number one! Woo-hoo!". Similarly, Luigi says "Yay for me, Luigi!" instead of "Phew, made it!", "Ho ho! Secret, shh." or "Yes! I'm a winner!".
  • Toadsworth acts as the minigames host, unlike later games where he's replaced with a Toad. This also is the only other mainline game where Toadsworth appears before he suddenly disappeared.
  • The design on Goal Poles is somewhere between that of the original Super Mario Bros. and all later games, as it retains the former's skull design (commonly mistaken for a peace sign) while introducing the white-on-black color scheme all future games would adhere to.
  • Interestingly, the new power-ups in this game all have a risk-vs.-reward aspect to them, rather than being a straightforward buff to the user. The Blue Shell's shell dash is fast and can kill almost any enemy, but is hard to control and can send the user into a pit; the Mini Mushroom lets Mario fit into small gaps, jump higher, and fall more slowly, but makes Mario struggle to kill enemies and die in one hit; and the Mega Mushroom lets Mario smash through any enemy or obstacle for a set time, but this is entirely dependent on the layout of the current level, as Mega Mario can't fit into small spaces.
  • Checkpoints were automatic upon reaching the middle point of the level, represented by a white flag with a mushroom symbol on it. Starting from New Super Mario Bros. Wii, checkpoints would be represented by flags physically in the level, initially black with Bowser's emblem before turning to the player character's emblem and color when touched. This would go on to become how checkpoints looked in future games outside the subseries such as Super Mario Galaxy 2 and Super Mario Bros. Wonder.
• Escape Sequence: The second half of World 8-3, where you are chased by a giant eel (Mega Unagi).
• Evil Elevator: The Ghost House Level in the Ice World Featured Two Ghost Coaster Platform, They begin to slowly rise when Mario (or Luigi) steps foot on them. As they ascend, they pass by collectible coins. They also pause to teeter back and forth as they ascend. Once they reach a certain height, ghost-coasters dramatically drop back down the corridor before slowly rising again, emulating the movements of drop towers.
• Fan Remake: As a testament to the game's legacy, even though the Mario vs. Luigi mode wasn't a full-fledged Co-Op Multiplayer mode like that of its follow-ups, it still was so unique and well made in its own right that fans liked it so much to make a remake of it in 2022, featuring online multiplayer for up to ten people, the Ice Flower and Propeller Mushroom as additional power-ups, five new stages, and more customizable rules.
• Family-Unfriendly Death: The apparent demise of Bowser in World 1 might be a little unnerving for some, which has him boiled alive in a pit of magma and reduced to a skeleton. He doesn't stay dead, however, as he shows up in skeletal form in World 8, and Bowser Jr. revives him properly for the final battle.
• Game of Nim: "Loves Me...?" in multiplayer is played as a Game of Nim. Every player can pick a minimum of one and a maximum of three petals from the flower during their turn, with the goal being to pick the last petal if the result will be "Loves Me" (which scores a point), or to get someone else to pick the last petal if the result will be "Loves Me Not" (which loses a point). Whoever has the most points after the round limit (3, 5, or 7) is the winner.
• Gameplay and Story Segregation: If the player uses the secret cannon in World 1 to go to World 5 early and avoids the first castle, Bowser will still be in his skeletal Dry Bowser form without explanation.
• Ghost Leg Lottery: A slightly edited minigame taken from Super Mario 64 DS has you drawing the horizontal lines as a face of Mario descends towards Stars (good) and Piranha Plants (bad). However, the lines you draw are only cleared after you win 5 rounds, quickly forcing you to contend with drawing new lines to make sure the ones you already have don't cause you to lose.
• Giant Mook: Aside from the returning Boss Bass, Big Piranha Plants, and Big Thwomps, the first now named Mega Cheep and can't eat Mario and/or Luigi from this game onwards, the second not being limited to pipes and attacks outside from them, and the third making its sidescrolling Mario debut, the game introduces Big Whomps, Giant Spike Balls, Mega Deep Cheeps, Mega Unagi, and Super Dry Bones, larger versions of the returning Dry Bones, Spike Balls, Whomps, and Unagi and the newly introduced Deep Cheeps.
• Gimmick Level: Bowser's Castle is filled with switches that turn the room upside down.
• Green Hill Zone: World 1, as per the series' norm, is a lush, grassy area.
• Grimy Water: The forest levels contain purple water, which is an instant death on contact.
• Ground Pound: This is the first 2D Mario game since Yoshi's Island to implement this move. Note that Mario and Luigi can only crush blocks when they're at least on Super level. When they're small, the pound is too weak to do so.
• Halloween Town: The first half of World 8, which consist of a decrepit valley overrun by Crowbers and Scuttle Bugs.
• Hoist by His Own Petard: Can happen to Mario in certain levels if the Mega Mushroom is not used with care. One level is made up of nothing but pipes and the majority of them can be broken with the Mega Mushroom. Break too many of them and you'll fall into the Bottomless Pit you've created.
• Homage: Several, to Super Mario Bros. 1. For instance, many sound effects from the original game are intact, such as coin collecting, enemy squishing, and block bumping. In addition, the Mega Mushroom Power-Up is colored just like the Super Mushroom from the first game. Also, one of World 7's levels from NSMB is extremely similar to 7-1 from Super Mario Bros. 3.
• Infinite 1-Ups: In homage to the original Super Mario Bros. 1, the "Koopa Shell Bounce" trick was shamelessly recreated.
• Interface Screw: In all ghost houses, the level progress bar on the touch screen is replaced by two ghost silhouettes staring at you.
• It's All Upstairs From Here: The point of the tower levels.
• Jungle Japes: World 4. The water is highly toxic, requiring Mario to ride Dorrie to avoid touching it, and the levels are overrun by Scuttlebugs, Wigglers and Paratroopas. This setting makes its first appearance in a platform Mario game since Super Mario World 2.
• King Mook: The boss at the end of the Castle in every World is a boss version of a common enemy.
  • Bowser, again is one to the Koopa Troopas, but the game takes it even further with the introduction of his undead counterpart Dry Bowser being that to the Dry Bones. Bowser Jr. is one to a lesser extent.
  • Mummipokey of World 2 is one to the Pokeys.
  • Cheepskipper of Work 3 is one to the Cheep Cheeps (who accompany him in the boss battle).
  • The Mega Goomba boss of Work 4 is obviously one to the Goombas.
  • Petey Piranha of World 5 is this to the Piranha Plants. It's even foreshadowed with the World 5 Castle ''highly populated'' with Piranha Plants despite being in an ice world.
  • Sort of Downplayed with the Monty Tank in World 6. While the Monty Mole clearly looks no different than his Mook counterparts, the fact that he takes 3 hits and is intelligent enough to man a powerful tank comes off as this.
  • Lakithunder of World 7 is one to the Lakitus.
• Lava Pit: Very frequent, especially in the castle levels. Making contact with it is a One-Hit Kill, though for the first time in the series, a Super Star can defy this and Mario will simply bounce off with a "SPLAT!" noise.
• Lethal Lava Land: The second half of World 8, only accessible after defeating Dry Bowser in what appeared to be the final level. One level has lava gradually rising, while another has spiral mountains erupting and launching melting rocks into Mario's whereabouts.
• Level in the Clouds: World 7, which houses several sky-themed levels where the only safe platforms are the clouds and the top of the green and red mushroom trees. Some of the other worlds also have specific levels set in the sky.
• Loves Me Not: In addition to the normal minigame returning from Super Mario 64 DS, NSMB1 makes a Game of Nim out of the "Loves Me...?" minigame in multiplayer by having multiple players trying to either get "Loves me", or stick the other guy with "Loves me not" by plucking 1-3 petals per turn.
• Magical Mystery Doors: There's a section of the game where you're perplexed by a series of doors. The only way to discover where they lead is to test each and every one of them. Fortunately, it's much shorter than most Magical Mystery Doors segments tend to be in NES games.
• Mickey Mousing: Whenever there's a vocalization in the main game track, the enemies will dance along with it, specifically Goombas will do a small jump and Koopa Troopas will look at the screen and shake their fists. When underwater, Cheep Cheeps will spin when a windchime is heard.
• Mini-Dungeon: As usual for 2D Mario games, the mid-world Tower levels, as well as the Ghost Houses.
• Mini-Mook: The Mini Goombas return in this game, only being encountered in the secret areas accessible via Mini Mario/Luigi and can be defeated by walking into them if they are normal sized.
• Misplaced Wildlife: Bizarrely, Snailicorn enemies are found in the icy World 5.
• Mordor: World 8, which hosts a bleak and decrepit scenery with haunted valleys, dark underwater levels, volcanoes and the final castle.
• Mythology Gag:
  • The game starts with a homage to World 1-1 from the first Super Mario Bros. 1, and there is a Bowser battle that can be defeated simply by breaking the bridge and dropping Bowser in the lava (or down a pit ala Super Mario Bros. 3), replacing the axe with a button.
  • Petey Piranha is sleeping before his boss fight and attacks when woken up. His very first appearance was Super Mario Sunshine, and the second fight with him was triggered by waking him up. Both instances of Petey sleeping may in turn be throwbacks to Super Mario 64, where all the Piranha Plants were sleeping and had to be snuck up on.
  • Then there's challenge mode, which is available after you beat the game, and enables Ratchet Scrolling like the original game.
• The New Adventures: It's all there in the title. This is the game that started a new generation of Mario 2D platformers.
• Nostalgia Level: The overworld-based level◊ from the Mario vs. Luigi mode is an abridged version of the first Super Mario Bros. 1' World 1-1.
• Painting the Medium: Underground shortcuts are represented by moving the top screen to the bottom, and vice versa. This also prevents you from using stored items.
• Palmtree Panic: World 3, which is set in a tropical island. Enemies like Cheep Cheeps and Bomb Skeeters are plentiful, and there's a Mega Cheep Cheep capable of eating Mario, killing him.
• Papa Wolf: Should you defeat his son first in the final battle, Bowser will Turn Red and barrage the boss lair with a spiral of fireballs.
• Pumpkin Person: Splunkins are basically waddling pumpkins that take 2 stomps to defeat.
• Reconstruction: Of the original 2D Mario sidescrollers, by bringing gameplay elements introduced in 3D Mario games in the interim to 2D Mario games alongside introducing various new power-ups, locations, obstacles, enemies and bosses to the franchise.
• Recurring Boss:
  • Bowser Jr. is the boss of every tower in the game, and is also one of the Final Bosses.
  • You also fight Bowser three times in the game: one as the first Castle boss in World 1, the second in his undead form in World 8's first castle, and the Final Battle in Bowser's Castle being slightly larger, much stronger, and fighting alongside Bowser Jr.
• Recycled Soundtrack: The Starman theme is the exact same as the Wing Cap/Invisibility Cap theme from Super Mario 64 with extra percussion added.
• Rubber-Band A.I.: Levels with rising lava have Rubber Band Lava. As long as the lava is on-screen, it will rise at a constant rate. As soon as it gets too far off-screen, however, it will catch up instantly. This is hard to notice normally, but can be seen by speeding upward as fast as possible, then scrolling slightly down and seeing that the lava has somehow caught up with you despite appearing to continue rising slowly.
• Save the Princess: It's a Mario game, saving Peach is the whole plot, this time with the twist that Bowser Jr. is the main antagonist not Bowser.
• Shifting Sand Land: World 2 is a desert, and as such there are quicksands, Pokeys and an oasis.
• Shock and Awe: Lakithunder, the boss of World 7, is capable of dropping lightning bolts to attack Mario. When hit twice, it will drop a series of bolts during Retaliation Mode.
• Shout-Out: Bowser's defeat is very similar to Crocomire's.
• Slippy-Slidey Ice World: World 5, a snowy grove. There are parts in which the snow is so dense that it makes traction more difficult, as well as parts where the ice has to be taken advantage of to slide through narrow corridors.
• Snowball Fight: One of the new minigames, Snowball Slam, has the players control different colored Yoshis in a snowball fight. Should there be three or more players, the players will be split into two teams.
• Snowy Sleigh Bells: The icy World 5's theme makes very heavy use of sleigh bells to instill a wintery feel to the track.
• Songs in the Key of Panic: When either player is only one Big Star away from winning a round in the Mario vs. Luigi mode, the music kicks up in tempo.
• Space-Filling Path: That block train in the second World 8 tower goes an extremely long way around the room in a ping pong path fashion...
• Springy Spores: A lot of levels, beginning with 1-5.
• Sprite/Polygon Mix: Many of the basic items and enemies with simple behaviors (Goombas, Koopa Troopas, and Boos) are rendered as 2D sprites. Mario, Luigi, the bosses, and other enemies with more complex patterns are rendered as 3D models.
• Super Not-Drowning Skills: Present, despite being absent in the 3D Marios that separated NSMB and its 2D predecessors and the one that separated the Wii version and the DS one.
• Suspend Save: You can only save at castles or by using Star Coins, though you earn the ability to save anywhere on the map after you finish the final boss.
• The Reveal: The boss of World 7, Lakithunder, was the storm cloud that attacked Peach's castle.
• Threatening Shark: Downplayed, this is the only other mainline platformer to have Sushi sharks as enemies. They only appear in World 1-A, can be dispatched as easily as a Cheep Cheep, and don't even try to seek out Mario and Luigi.
• Toggling Setpiece Puzzle: The first castle of World 8 features rails whose platforms (lifts) can have their positions switched with red-and-yellow switches. For example, if a lift is placed on an upper rail, pressing a switch will teleport it to the lower rail. Therefore, before you stand onto a lift (which will make it move forward), you have to decide its position (and potentially grab the castle's Star Coins, including the last one which requires a not-very-obvious way to spawn a lift into the rail right below the Boss Room's door).
• Took a Level in Badass:
  • Later fights against Bowser Jr. has him hiding in his shell every time Mario (or Luigi) attempts to jump over him, ensuring that the player must find other ways to defeat the Koopa Prince (i.e., Fire Flower, knocking a shell back at him, or simply using the Mega Mushroom). It's also worth noting that he covers his mouth with his bib to look more intimidating, showing how much more serious he is when taking on the Mario Bros.
  • The later fights against Bowser are a lot harder than his World 1 bout, where there is no platform this time helping Mario or Luigi jump over him to reach the switch. His Dry Bowser form (being an undead Koopa) is complete immune to fire, meaning that the Mario Bros. can only rely on either a timed jump (or a Mega Mushroom) to defeat him. His Final Boss battle has him much larger and sporting new attacks, especially when he goes Papa Wolf after Mario or Luigi defeats his son first (not to mention him taking more hits from the Fire Flower before going down).
• A Twinkle in the Sky: Using a cannon on the map sends Mario flying into the sky before disappearing into a sparkling star.
• Underwater Level:
  • All worlds except 2, 5 and 7 feature at least one underwater level, with the earliest one being World 1-A. Oddly, despite its water theme, World 3 does not have a lot of them, featuring only two.
  • World 8 has an odd example: an underwater level with a cavern-like background and the underground music playing rather than the underwater music.
• Unique Enemy: There are several kinds of enemies that only appear in one level each:
  • Whomps only appear in world 3-Castle. Most of them stand in the background and wait for Mario to appear, and there is only one single Big Whomp, who walks across a platform instead.
  • World 4-4 contains the only five Balloon Boos in not only the game, but the entire franchise. They are like regular boos, except they will inflate themselves until they reach maximum size when Mario looks at them, and deflate as they chase him when he looks away.
  • Snow Spikes only appear in World 5-1.
  • World 6-6 contains the only three Chain Chomps in the entire game.
  • Small Wigglers known as Squigglers only appear in the pipe maze of World 7-A.
  • World 8-7 is the only course where Fire Bros and Sledge Bros appear.
  • There are twenty-one Kab-ombs, and they all appear in World 8-8.
  • The icy level from the Mario vs. Luigi mode contains the only blue-shelled Koopa in the game. Stomping it lets you obtain the Blue Shell powerup, making it the only way to 100% reliably get this item.
• The Very Definitely Final Dungeon: After a fake-out in World 8 where the game keeps going after you clear what seems to be the final castle stage, you eventually reach a giant Bowser castle larger and more detailed than any other in the rest of the game. This one is the true final stage.
• Vine Swing: Some levels in the jungle-themed World 4 feature vines Mario and Luigi can use to swing in order to reach a far spot. This is important due to said levels being partially flooded with lethal Grimy Water.
• Walk on Water: Mini Mario is light enough to walk on top of water as long as he doesn't stop moving.
• You Shouldn't Know This Already: A rare aversion in that the game only tells you that you can play as Luigi by holding the shoulder buttons when selecting your file after defeating the Final Boss, but there's nothing stopping you from doing it before beating the game if you already know that.