Shout-Out examples in Undertale.
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Anime & Manga
- To JoJo's Bizarre Adventure:
- Mettaton EX has a heart-shaped belt buckle and poses a lot, one such pose being a pelvic thrust with the arms hanging at the sides, like Dio Brando.
- The Mad Dummy screams and laughs a lot and throws knives at you. It even says "Futile! Futile! FUTILE!" and "Feeble! Feeble! Feeble!", bringing to mind DIO's famous "MUDA MUDA MUDA!" Battle Cry and "Hinjaku, hinjaku" Catchphrase, respectively.
- Mad Mew Mew seems to be a wholesale reference to DIO. In addition to being the same ghost as the Mad Dummy, she also states she's attempting to merge fully with the rest of her body by the head (not unlike DIO's head merging with Jonathan Joestar's body) and also makes an expression
◊ resembling DIO's memetic "But it was me, Dio!" face◊.
- Mad Mew Mew seems to be a wholesale reference to DIO. In addition to being the same ghost as the Mad Dummy, she also states she's attempting to merge fully with the rest of her body by the head (not unlike DIO's head merging with Jonathan Joestar's body) and also makes an expression
- Using the Punch Card in battle displays the message "ORAAAAAAA!", a reference to Star Platinum's Battle Cry when using its Rapid-Fire Fisticuffs.
- Try calling Undyne's number on the SAVE Point in Hotlands with two knights nearby. She'll make a pretty pinpoint description of an anime she once saw purely for research purposes about a warring human who could mind control others. (In-universe, it's a totally different anime.)
- Madjick's battle dialogue consists of various "magic words" phrases ("Abracadabra", "Hocus pocus", "Please and thank you"), among which are "Tinkle tinkle hoy".
- Alphys's fan rage about one of her favorite works, Mew Mew Kissy Cutie, having a horrible sequel. Even though the fictional anime as described has only the name, a catgirl, and kissing having magical properties in common with the real manga, this is strongly reminiscent of the fan rage over Tokyo Mew Mew à la Mode. This is further accentuated by Mad Mew Mew, a sentient Mew Mew Kissy Cutie doll in the Nintendo Switch and Xbox One ports who resembles Ichigo, the lead character of Tokyo Mew Mew.
- While Undyne references a lot of Hot-Blooded anime heroes, Undyne the Undying is a Super Mode achieved through a combination of a pure heart, incredible strength, and a desperate need, much like a Super Saiyan.
- During Papyrus's Boss Battle, he confidently predicts that the King will trim a hedge in the shape of his face. This likely references a scene in Black Butler where Grell has trimmed a bunch of hedges to look like skulls, which is even set to similar-sounding music.
Film
- The monster Loox has a family name of Eyewalker, making its full name Loox Eyewalker. As an additional movie reference, Loox's internal filename is "Mike Wazowski".
- In the room where Mettaton disguises multiple objects as bombs, he describes a scene in his upcoming movie where he is showered with rose petals.
- If you call Papyrus from Hotland, he’ll express disgust over the steam grates and wonder what would happen if you were wearing a dress.
Homestuck
Given that Toby Fox composed music for Homestuck and worked on Undertale in its author's basement, this comic is bound to have a folder of its own.
- The $1000 Kickstarter reward was "Your Fantroll becomes Canon".
- Aaron, a flexing musclebound seahorse that can attack by sweating on you, definitely gives off some serious Equius vibes. Additionally, even though Temmie was inspired by the artist of the same name, the Homestuck connection is supported by the Aaron and Temmie encounter in Waterfall, which bares a striking resemblance to Equius and Nepeta.
- There's a living rope on fire with the name Pyrope.
- The songs "Hopes and Dreams" and "SAVE The World" both have the piano motif from Homestuck's long-teased Hidden Track "Penumbra Phantasm" layered in the background, which is itself derived from "Doctor," something Toby himself would later confirm in the 10th Anniversary stream of Asriel's fight.
- Migospel, Migosp's replacement in the Hard Mode, seems to be a reference to Gamzee. It's a "messed-up clownbug" with a rather religious sounding name, and one of its battle lines is "Honk. HOOONK!", which is extremely similar to Gamzee's honking while sober.
- The areas of the Underground resemble certain areas in Homestuck. The Ruins resemble Derse, Snowdin resembles the Land of Frost and Frogs, Waterfall resembles the Land of Wind and Shade, Hotland resembles the Land of Heat and Clockwork, and the Last Corridor resembles Prospit. Moreover, the theme for Hotland is called "Another Medium", as a reference to the mystical dimension Sburb locations exist in.
- In [S] Wake, Aradia suspends Bec Noir in time, rendering him unable to continue his rampage through the trolls' session after he's done killing most of the cast, at the cost of being unable to move herself. This is the exact same thing Sans tries to do to the player — except it works in Aradia's case, as it buys time for the remaining trolls to escape to the meteor. The song playing in both instances? Megalovania.
- The blueprints for a strange machine in Sans's basement, and they look like the blueprints drawn by Caliborn, who happens to be another round-faced skeleton with a flashing-eyed Super Mode.
- Flowey's laugh is a stock Warner Bros sound effect also used in The Lordling, a theme Toby wrote for Caliborn. While Caliborn is similarly a Psychopathic Manchild who sees the world as a game to win, Flowey is much more of a Tragic Monster.
Literature
- The Check description for RG01 and RG02 on the Genocide Route is taken from the book Kitchen by Banana Yoshimoto, as seen here◊.I see two lovers staring over the edge of the cauldron of hell. Do they both wish for death? That means their love will end in hell. I couldn’t stop laughing.
- Papyrus is an animated skeleton whose speech text is written in all capital letters, just like Death.
Live-Action TV
- Vegetoid's flavor text, "Vegetoid's here for your health.", is intended as a reference to the Dr. Steve Brule sketches from Tim and Eric Awesome Show, Great Job!, in which Dr. Brule recommends bizarre treatments "For Your Health".
- If you keep petting Lesser Dog, a piece of flavour text reads "Lesser Dog has gone where no dog has gone before".
MOTHER series
Being greatly inspired by the Mother series, down to having a striped shirt-clad protagonist, the game indeed contains an abundance of references to it.
- As noted under Sdrawkcab Name, Mt. Ebott is a mountain named after the game's creator. This is likely to be a reference to Mt. Itoi from the EarthBound Beginnings.
- Papyrus's costume (the chest part of it, at least) bears the Starman insignia, down to being where it is on the Starmen.
- The similarities really kick in for the endgame. At New Home, you walk through a grayscale version of Toriel's house while monsters relate the story of Asgore, Toriel, and their children to you, which is very reminiscent of the way flashbacks are handled in Mother 3. Later, the Neutral Route's final boss nearly quotes Porky's taunt in EarthBound (1994) for the player to cry out for help verbatim... which is exactly what happens. Each of the other six human souls answer your call for help and assist you in the battle.
- The Pacifist run's Final Boss is nearly the same concept as the final battle in Mother 3. Both are battles that are not only impossible to lose, but also tug on your emotions by having you fight someone you love in an "I Know You're in There Somewhere" Fight. You fail to save that special someone in the end, and as a result you witness them either become loveless again or die, respectively. Both games have yellow flowers as a major motif and more-or-less a plot point as well.
- With his striped shirt, kind personality, adorable design, close relationship with his family, association with yellow flowers, and relentlessly tragic existence, Asriel is pretty much a fluffier version of Lucas. The two boys are even described as "crybabies" multiple times during both of their games.
- Asriel can also be seen as a Giegue/Giygas Expy. They start out living a normal life with their parents until one of their relatives brings about the dissolution of their families (George steals the aliens' PSI technology while Chara devises a plan to "free" monsterkind), kicking off a chain of events that leads to them losing their minds and becoming unrecognizable shells of their former selves.
- The battle music for the Amalgamates uses samples taken from EarthBound (1994)'s Cave of the Past theme and the noises that Giygas makes. The Amalgamates even glitch out like Giygas does, and the Memoryheads resemble him. Similarly, the track "Ghost Fight" samples the sound effect for Venus' singing voice as well as the heavily distorted version of "Good Old Days", the theme song for The Little Rascals, that plays in Jackie's Cafe.
- The Genocide Route's Arc Words, "But nobody came.", seem to be another reference to EarthBound, where the phrase is the message displayed when an enemy attempts to call reinforcements, but none show up. Made even more poignant in context - in EarthBound, the game can state, "<The enemy> called for help! But no one came." This is repeated almost verbatim throughout the game, particularly in reference to Flowey and the Amalgamates in the True Lab, all of whom died in one way or another and Came Back Wrong.
- Undyne's battle songon the Genocide Route is called "Battle Against a True Hero," a reference to the unofficial enemy track names in EarthBound, usually called some variant of "Battle Against a ___ Opponent".
- Some of the True Final Boss's attacks seem to be EB references, too - STAR BLAZING in particular really, really resembles PSI Starstorm. The name itself comes from the dub of Space Battleship Yamato, which was localized as Star Blazers.
- Toby Fox is represented by a small white dog, not unlike Ruffini — a small white dog seen in Onett's drugstore who got "possessed" by the game designer to give you some gameplay tips.
- If you end up fighting Sans, his attacks make your HP damage work exactly the way it did in EarthBound: rolling back gradually.
- The snoring of the guests in the Snowed Inn sounds rather like Buzz Buzz's buzzing.
- Although the Real Knife was named after a rumor caused by some Foreshadowing in the demo, it conveniently parallels the Real Bat weapon found at the end of Mother 3. You even find it inside a gift box, which are used in place of treasure chests in the Mother series.
- At the end of the Genocide Route, Sans takes note of the beautiful day and says "On days like these, kids like you..." and you half-expect him to toss out a comment about playing Nintendo games.
- If you try to use the Bird That Carries You Over a Disproportionately Small Gap while carrying an umbrella, the game replies "Umbrellas and birds... A bad combination." This greatly recalls a similar message that appears in EarthBound if you decide to backtrack to Happy Happy Village and try using the Carrot Key on a cow there.
- In the Ruins, there's a gag with a frog complaining about the player skipping his dialogue with X. That was also done in Mother 3.
- The "WELCOME TO HOTLAND" sign resembles the wall in Lumine Hall that broadcasts Ness's thoughts.
- Papyrus's distinctive "Nyeh heh heh!" laugh could be based on Fassad's "Nwehehehe" laugh from Mother 3.
- The Vegetoids that just sit there in the ground and wait for the player to approach them (and perhaps take a bite out of them), unlike most Undertale monsters, are rather similar to the Yammonsters of Mother 3.
- Chara's theme sounds very similar to Giegue/Giygas' theme from the original MOTHER/Earthbound Beginnings.
- Likewise, "Once Upon a Time" was inspired by "Mother Earth."
- Combinatorial Explosion can result in the line "The Dog Salad was absorbed by the darkness." This is a reference to a much more serious moment in Earthbound where Paula's prayers go unanswered (which is similar to what happens in the Photoshop Flowey battle).
- In its bridge, "Snowy" quotes a short six-note phrase of music colloquially known as the "Mitsuda Lick," likely as a reference to "Snowman" from Mother 3.
Music
- If you return to Onionsan's room and talk to him again, he'll mention that he's starting a band called the Red Hot Chibi Peppers.
- In addition to being taken from the Cave of the Past theme in EarthBound (1994), the ethereal vocal sample in "Amalgam", the Amalgamates' battle theme, is sourced from the Lyrical Cold Open to "Deirdre" by The Beach Boys.
- In a similar vein, by sampling the theme for Jackie's Cafe, "Ghost Fight" indirectly samples "Good Old Days" AKA The Little Rascals theme song.
- Toby Fox has confirmed that the arrangement for the song "Hopes and Dreams" was inspired by the works of Anamanaguchi.
- If you don't touch any green tiles during the tile maze section of Mettaton's opera, Mettaton will say "YOU NEVER STEPPED ON A GREEN TILE. ... AND NOW YOU'RE GOING TO DIE."
Theatre
- If you kill Papyrus on a neutral run, his head will fall off and he'll hold it in his hand. He exclaims "ALAS, POOR PAPYRUS!" before he turns to dust, referencing the famous line from Hamlet.
Video Games
- Papyrus' dating sequence plays more like an Ace Attorney game than a Dating Sim. The music is basically the Undertale main theme pretending to be "Turnabout Sisters" and "Pursuit ~ Cornered!", respectively. There's a part where you have to "perceive"note something on Papyrus' sprite à la Apollo Justice, and even a "breakdown" sequence at the end.
- At a given moment, he says "WHAT YOU JUST SAID IS INVALID!!!", which is essentially the same as "OBJECTION!"
- The "dating UI" Papyrus brings up also has a population bar and a crime map that reference the SNES version of SimCity.
- You can choose to describe anime as cartoons, but "with gun's." Barkley, Shut Up and Jam: Gaiden uses a similar incorrect pluralization every time it refers to "gun's" as an intentional "Blind Idiot" Translation.
- Brandish:
- The concept of a human falling down a hole into a lost underground kingdom is a Whole-Plot Reference to the first game in the series.
- The Ruins are named after the area of the same name.
- Asgore is stated in the supplementary art book to have originally been based off of Brandish's own monarch, Bistall/Berebus.
- "MEGALOVANIA" first started out as a blend of "Megalomania" from Live A Live, and Brandish 2's final boss theme, "Gadobadorrer" ("God-Badorrer" if translated properly.)
- The Dimensional Boxes are taken directly from Brandish, right down to the name (at least in the SNES port; the PSP remake, The Dark Revenant, localized it as "Otherworld Box").
- The shop UI is based on the one in Brandish, including the presence of the TALK button.
- As mentioned in the art book, the line "It's too dark to see near the walls." in the introduction of Alphys's lab is a reference to a similar line in Brandish.
- One of Aaron's lines is "Education? Hobby? Talent?", a reference to a similarly musclebound and underdressed boss in Breath of Fire II.
- Chrono Trigger:
- The track that plays before you fight Undyne the Undying is titled "But the Earth Refused to Die", evoking the text of Chrono Trigger Game Over screen, "But the future refused to change." Furthermore, the narration in that same battle says "The wind is howling...", which is similar to Magus's declaration that "the black wind howls."
- Word of God says the CORE's interior design was based on the Ocean Palace.
- The bell that rings in the Last Corridor before Sans's judgement in all routes barring the Genocide one sounds almost identical to Leene's Bell.
- In the Switch version of Undertale, examining the blue and red door before you can open it will say that it's closed by a mysterious seal, while an ominous piano jingle plays. Chrono Trigger does the same thing when you try to examine a black chest before you can open it.
- During Mettaton's news report, Mettaton will say "THIS NEWS REPORT... IS TURNING INTO A DISASTER REPORT!" referencing the game of the same name.
- Final Fantasy:
- The opening of Mettaton's dramatic opera trap is very similar to the Opera scene from Final Fantasy VI. The two themes related to it also use very similar instruments. The background music for the following scene is also highly reminiscent of the background music for the battle that follows FFVI's opera scene.
- Encounter Undyne after you've befriended her in a previous playthrough, and she'll end her pre-battle speech by defiantly proclaiming that she, Undyne, will knock you down.
- One of Asriel's attacks is the HYPER GONER, named after Kefka's Goner attack in the Super Nintendo version of Final Fantasy VI.
- Mettaton's Pop Quiz includes one question asking the player to name the favorite ice cream flavor of a character in a fictional series, a random piece of trivia not pointed out anywhere before and never mentioned again. Frog Fractions presents the player with a similar question, though that game, unlike Undertale, provides no definitive answer.
- The monster Lemon Bread is a reference to Melon Bread, a boss from Gunstar Heroes. One of its attacks even resembles Melon Bread in appearance.
- When Toriel bakes you the Butterscotch-Cinnamon Pie, she mentions that she thought about baking a snail pie, an obvious reference to Illusion of Gaia.
- Ikaruga:
- The human character Frisk seems to be a carbon copy of Shinra, a similarly dysfunctional protagonist of that game.
- Photoshop Flowey shares alot of similarities with Stone-Like, particularly the ability to destroy the world with Bullet Hell capabilities (as showcased by Stone-Like in Radiant Silvergun). Unlike Stone-Like., which was destroyed even under the Dot Eater achievement, Flowey is redeemably spared in the True Pacifist Golden Ending.
- The Legend of Zelda:
- Mettaton prefaces one of his quiz questions with "LET'S PLAY MEMORY GAME."
- A "Croissant" that awfully resembles the Power Bracelet from The Legend of Zelda: Link's Awakening, to the point that even the protagonist mistakes it for one before realizing what it actually is.
- After Asgore destroys the MERCY button, his design shows a lot of influence from Ganon in the early Zelda games, particularly his trident.
- Live A Live:
- According to Word of God, Sans' boss theme, "MEGALOVANIA", is a reference to the boss theme of Odio, "Megalomania".
- The storytelling structure of Undertale owes quite a bit to Live A Live in general. Oboro's chapter in Live A Live also changes completely depending on whether you chose pacifism, a neutral route, or a violent approach.
- Flowey's backstory of being manipulated by a close friend and mistaken for a murderer before deciding to become a villain is parallel to the story of Oersted.
- In the art book, Toby is mentioned to have cited the Sinistrals from Lufia as inspiration for Asgore's design (Amon's portrayal in Lufia & The Fortress of Doom is very similar).
- At one point during the Mettaton News segment, Mettaton will say: "EVEN MY WORDS ARE BOMBS.", with his words promptly falling to the floor and exploding. This is a clear reference to Princess Peach losing her voice and instead getting an explosive vocabulary in Mario & Luigi: Superstar Saga.
- A few of the monster's quotes are the same as some of the enemies' from Monster Party, such as the Loox's "Don't pick on me" and "Finally someone gets it".
- OFF
- Papyrus was confirmed in the official Undertale art book to have originally been inspired by Dedan, which you can see a little in his appearance, though Papyrus was a much more mean-spirited character back in the early development stages. In fact, Undyne seems to have taken on these characteristics.
- The theme for Napstablook, "Ghost Dance," was also directly inspired by the repeating jazzy battle theme "Pepper Steak" from OFF. The fact that the associated character is a ghost is likely not a coincidence.
- The monster in the lower-right hand corner of Grillby's looks uncannily like Spinda.
- Word of God said that the whole concept of being able to spare enemies instead of killing them, as well as each enemy having a unique method of doing so, was inspired by the Shin Megami Tensei games.
- Migosp, who's an insect-like monster, has quotes that reference the Zergs, insectoid aliens from StarCraft. Quotes include "HEED THE SWARM", referencing the Zerg swarm, and "OBEY THE OVERMIND", referencing the Overmind who controls the Zergs.
- If you examine the oven during Mettaton's cooking show, Mettaton says "MTT-BRAND OVENS CAN REACH TEMPERATURES UP TO NINE-THOUSAND DEGREES!"
- If you get to the very end of Mad Mew Mew's attacks, by doing a No-Damage Run on the usual attacks, you will be greeted with 80s slang that was used to name Super Mario World's special stages.
- The seven Human SOULs are similar to the eight Pure Hearts from Super Paper Mario, right down to sharing colors. Their role in the Photoshop Flowey battle is also near-identitcal to that of to the Pure Hearts in the Super Dimentio battle.
- The high school sequence starring Mettaton seen in the UNDERTALE 10th Anniversary livestream is one long send-up of Tokimeki Memorial.
- The song that replaces "Cool Beat" when sleeping at the MTT Resort in the 10th anniversary livestream is a short breakcore piece called "Ultranap", referencing ULTRAKILL's frequent featuring of breakbeats in its soundtrack.
- Yume Nikki:
- The Waterfall area has similar features to Yume Nikki's Docks area.
- Some of the NPCs in Undertale are inspired by those in Yume Nikki. This includes the nebulous "Mysteryman", whose appearance looks almost exactly the same as that of Uboa.
- Chara's "scary face", which they show if you try to refuse destroying the world with them at the end of the Genocide Route, also resembles Uboa's face, complete with a similar droning sound effect and the screen shaking. Not to mention that both cases involve superficially cute characters turning into freaky-looking monsters.
Touhou Project
- Just like in Touhou, a human in Undertale resolves issues with monsters via Bullet Hell fights. One of Touhou's defining traits is personalized bullet pattern attacks which highlight the individuality of each character, and Undertale has this in spades.
- Undertale's premise of a monster society sealed away by a barrier is similar to Touhou's youkai being sealed away from the outside world by the Great Hakurei Barrier. Both occurred as a result from fights with humans.
- Toriel's dress (deep blue/purple waistcoast, white sleeves and a triangular emblem) is identical to that of the Highly Responsive to Prayers final boss Sariel. It is also likely not a coincidence that True Final Boss Asriel also looks like Sariel, and is similarly named after an extremely powerful angel from Christianity.
- Some properties of the monsters, particularly them being Made of Magic and prone to emotional or spiritual attacks, is shared between the series. This is far more dangerous and destructive for the monsters of Undertale, though.
- Undyne's battle themes use the trumpet soundfont closely associated with ZUN, Touhou's creator and composer. Other songs like Heartache and ASGORE have sections with similar composition technique. Toby Fox stated that the Touhou series of video games was one of his greatest musical influences growing up and is very familiar with ZUN's music style. Similarities might have been intentional, as the Undyne No Mercy fight especially has wide screen Touhou-esque Bullet Hell patterns.
- Photoshop Flowey's green and yellow heart themes sound exactly like Hartmann's Youkai Girl and Bad Apple!! respectively.
- Word of God has implied the Asriel fight is mainly inspired by Marisa Kirisame, whose signature bullets are rainbow stars and lasers.
- STAR BLAZING may be derived from Marisa's "Blazing Star".
- SHOCKER BREAKER functions like Marisa's vertical lasers with indicators at the bottom of the screen, such as in Light Sign "Earth Light Ray".
- CHAOS BLASTER and Asriel's final desperation beam are a dead ringer for Marisa's Love Sign "Master Spark". The former resembles the normal version whereas the latter resembles the "Wide Master" variant from Impossible Spell Card.
- HYPER GONER is similar to the final attack of Subterranean Animism's final boss, Utsuho's "Subterranean Sun".
- Asriel: God of Hyperdeath's design may be inspired by the angel of death Sariel from Highly Responsive to Prayers.
- Tsunderplane dons a bonnet commonly worn by Touhou characters such as Remilia Scarlet and Yakumo Yukari. The method of sparing it resembles Touhou's graze mechanic.
Webcomics & Internet culture
- At the end of the final fight on the Neutral Route, the boss makes an utterly legendary Trollface.
- Sans and Papyrus being named after typefaces is a reference to the webcomic Helvetica. Due to the game it inspired being way more famous than the comic, it is both Parody Displacement and a Colbert Bump for the latter.
- Several to Gigi D.G.:
- If your character is named Gigi, Gugu, or Drak, the item name of 'Steak in the Shape of Mettaton's Face' will be shortened to 'Fsteak' in your inventory.
- The rabbit shopkeeper in Snowdin, marked "QC" in the files and fully referred to as such in Deltarune, has the inversed initials of Cucumber Quest, Gigi's RPG-inspired webcomic starring rabbits.
- In the art book, Toby states that one of Flowey's inspirations was Face from NES Godzilla Creepypasta.
- One NPC in the New Home section of the 10th Anniversary stream, the "Arbiter Crab," seems to be a reference to the King of Town from Homestar Runner. They have a very similar red-and-white robe and bushy mustache to the KOT, and when talking to them, they say "Doo-hoo-hoo," which the King says when happy or worried. Toby also calls them "King of Town" when approaching them during the stream.
Western Animation
- The scene where the Mad Dummy is introduced features a recreation of the sting from the episode "Bad Day at Peril Park" of the Mega Man cartoon, where Guts Man is discovered disguised in a kangaroo costume; this "Guts Man's Ass" moment was a meme in the YouTube Poop community for a while. The music that follows is a recreation of the boss introduction of the earlier games in the Mega Man X series. The Mad Dummy's sudden coming to life and hovering attack also suggest the lamp at the beginning of EarthBound Beginnings.
- Papyrus gives a "NYEH HEH HEH" laugh, much like Skeletor from Masters of the Universe.
- On the No Mercy path, the speech about Sans and Papyrus not needing the player's help to "have a good time" after all and subsequent warning that the player will "have a bad time" if they persist in their Omnicidal ways is highly reminiscent of Thumper's spiel about skiing and "having a good time" from the South Park episode "Asspen":Thumper: "You French fry when you pizza, you're gonna have a bad time."
Sans: "if you keep going the way you are now...you're gonna have a bad time." - The Thundersnail race and its turnout are a direct reference to "The Great Snail Race" episode of SpongeBob SquarePants.
- "Your Best Friend" is "The FUN Song" slowed down.
- Alphys saying "Oh no" followed immediately by Mettaton bursting through a wall and saying "OHHHH YES!" evokes a Running Gag in Family Guy where repeated cries of "Oh no!" will almost inevitably invite the Kool-Aid Man to burst into the scene in his trademark fashion and utter his Catchphrase, "OH, YEAH!"
- Mettaton's box form resembles the coin-operated robot cooker from the Wallace & Gromit short film A Grand Day Out, as confirmed by the artbook.
- " Huh!? Blueprints...!? Literally. It's white paper, but covered in little blue pawprints... Wait... Blue pawprints... Could it be a clue!?" The blueprints themselves could also be a reference to the show's Pilot, "Blue's Prints".
- The training dummy outside Undyne's house says, "It's a living."
- When Undyne meets Toriel for the first time: "Hey, Asgore, is that your ex?...That's rough, buddy." For context...
- In the Undertale 5th Anniversary Alarm Clock, Asgore mentions getting stuck in the chimney, along with someone drawing a face on his rear end.
- Ice Wolf is a rather cool-headed character who has a Third-Person Person way of speaking, much like Ice Bear, complete with both names beginning with "Ice"
Other
- Flowey's voice clips and the Amalgamates' laugh are distorted samples from a 1960s McDonald's commercial.
- If you spare all the dogs, you find them later at Grillby's playing poker, a reference to the "Dogs Playing Poker" series of paintings by C. M. Coolidge.
- Napstablook is named after Napster, a defunct file-sharing service that was popularly used during its lifetime to illicitly share music. Examining the computer in Napstablook's house will say that it's open to a music-sharing forum.
- One of Papyrus's many guesses as to what the "L" on Hotland's elevators stands for is "lasagna". According to him, he doesn't make lasagna anymore because the Annoying Dog always eats it, then "retreats into a shallow blue box, covers itself with a blanket, and sleeps."
- Sans' self-titled theme is based on the melody from "In and Out Crowd", an animated short by Sally Cruikshank that aired on Sesame Street.
- The Nice Cream salesman is a blue rabbit monster, a visual reference to the Blue Bunny ice cream brand.