In Hearts Like Clockwork, according to a document file in Rin's computer, Evillious Chronicles exists as an old play dated to the 21st century by an author whose name was long lost to history (the game is set After the End in 23rd century Japan). Fittingly, Rin and Len performed the "Daughter of Evil" part for their last day in middle school as Riliane and Allen.
Kara of Rokyn: The main character is the lead actress in the "Kal & Lyla" film, whose shooting is the final story arc's central plot.
The South of Nowhere story, Romance on the Set Spencer and Ashley (and many of the other characters) star in a teen drama called North of Somewhere and meet during production.
The Skyhold Academy Yearbook series has several examples in the form of various characters writing Real-Person Fic about themselves and each other. If Varric Tethras isn't the one writing it, he's usually the one reading it out loud to other characters (and thus to the reader).
Superhero RPF is a fanfic about fanficers so it has a lot of fanfics in it. Most just referenced by their title and summaries, except For Asgardia!, by a guy going by the username Sassgardian, from which there are excerpts all around the fic. It gets him accused of Draco In Leather Pantsing for his heroic interpretation of Loki, and when his identity comes out, he is in fact Loki writing Self-Insert Fic.
Tales of Karmic Lies Aftermath features Ladybug: Miraculous Journey, an official movie based off of the titular superheroine's adventures. Marinette and the rest of the current Team Miraculous are involved with the project, and several chapters focus on the movie's development and plotline.
The project is used by several characters as a way of dealing with various issues. Nooroo, for instance, deals with the trauma of being used for Hawkmoth's evil purposes in a rather unusual fashion: he insists that his movie counterpart become The Man Behind the Man, an Evil All AlongManipulative Bastard playing Hawkmoth for his own ends. He does this specifically because he knows a Control Freak like Gabriel would take even a fictional counterpart being depicted as somebody else's pawn as a personal insult.
The movie also naturally diverges from reality in various other ways, such as how it reflects the public's belief that Adrien/Chat Noir was secretly working with his father.
The United Heroez have their own movieverse; it's mentioned in passing that not all of the entries have met with their approval, such as the disastrous Knightowl V Majestia: Dawn of the United.
Advice and Trust: In chapter 8, Shinji and Asuka watch a show based on an Adeptus Evangelion campaign the author takes part in. Asuka describes it thusly:
"You wanna plop down and watch another episode with me, Misato? Shinji and I have been watching it lately. It's like someone heard about NERV, took a lot of drugs, and then tried to make it a comedy-drama-angst-romance with an ensemble cast of traumatized lunatics. It's a cheesy giant robot show, but a lot of fun. Everyone in it is pretty hot, too. Especially that Akram guy. Yow."
Cheating Death: Those That Lived: Panem is a fan of the Romantic Comedy sitcom, Fiona and Lawrence which is the most popular show besides the Hunger Games, and possibly one of the longest-running television shows in Panem.
Farce of the Three Kingdoms has the gripping reality TV drama Real Concubines of Wu, which is popular in Wei and Shu. Unfortunately, the narrator doesn't care about Wu, so all we see are Noodle Incidents.
The Great Snowball Battle Trilogy: Toji's little sister Sakura is a big fan of a popular TV-Series called Genesis, so that her brother's friend Kensuke got her the Collector's Edition with all the seasons and figurines to keep her entertained during her hospital stay.
Freddy Freeman: "Denny, if it's about the new comics, they don't come in today. You know that, right?" Denny Smith: "Right, Mr. Freeman. I just want to make sure you know to put the right ones back for me." Freddy Freeman: "Sure. Superman, Uncle Scrooge, Crime Does Not Pay, and Frontline Combat. They'll be here for you, Den, when they get here. If they get here."
The Ikaris: The "Super Gendo Super Show", created by the PR department to make people more aware about Commander Ikari. It is like Evangelion on crack with a healthy helping of Super Robot Genre and tokusatsu tropes. They are making lunchboxes, too.
In Junior Officers, Deborah is a huge fan of an anime called Intergalactic Imogen.
The Legend of Genji: Kalsang is a diehard Fan Boy of the sci-fi TV series Starbenders: A Journey Through Space to the point where he's seen every episode, constantly shares his fan theories with his family, and has even named his pet sky bison Aimee after one of the show's characters. Luan is also a fan of Starbenders and has personally met the show's cast.
In My Huntsman Academia, Izuku has an entire collection of comics titled, "The Adventures of the All Mighty Huntsman", which are a loose adaptation of Toshinori's various adventures. There's also a TV show based on the comics, in which Toshinori's voice is impersonated by a guy named Chris Sabat.
Nobody Cared: Draco is a fan of the book series Warlock Solomon Adventures, which is about a heroic warlock who is trying to defeat the vampire lord, Lord Singe. He quickly gets Harry into the books as well. The two discuss the events of the most recent book while waiting for Professor McGonagall's hearing to be over.
Oni Ga Shiku Series: There is a movie franchise called "Yakuza Sunset". Izuku and All Might are huge fans. There is a Running Gag of everyone thinking that Izuku in his hero costume (a leather semi-formal suit) looks like he walked right out of those movies (though it should be noted that the movies are not his source of inspiration).
Futari wa Hearty Pure. The Cures (and also most people at their school) are big fans of the show, and Lapinyuu becomes part of the cast, playing a Shiny Luminous parody.
The two shows that helped Chloe and Chiara's father Theodore become a trampoline fetishist, Bounce and Thud, also count.
The Raven & the Owlet: The Good Witch Azura from the original show comes up frequently, but the fic introduces a few other Boiling Isles-specific media:
Titan: Beyond The Stars is a science fiction graphic novel about the people of the Boiling Isles converting the Titan's skull into a spaceship to escape the end of the world. Boscha is a fan, and gives an omnibus to Luz, who quickly becomes hooked.
Luz and Amity spend their first date at a dinner-theater watching Tairbith, a tragi-comic revenge play about a prince trying to avenge his late brother, only to run into all sorts of Slapstick in the process culminating in a Hamlet-esque bloodbath.
Luz and Amity on sepparate occasions watch the second "Avalar White" movie (it's unclear if Avalar is the main character or the director) with Boscha. Apparently the first movie was a mystery, while the second leans more on action with the mystery being cleared up halfway through and the rest being a thriller. Amity prefers the first movie, Boscha prefers the second, and Luz has only seen the second and so can't decide yet.
Homura's favorite show as a child, and still is even as she has gotten older, is "Holy Quintet's Joyous Friendship", an old magical girl series that aired decades prior. She is very protective of it, for it was a source of happy memories for her while she was growing up in the orphanage, to the point that she will get angry at those who badmouth it.
Super Magical Girl Cosmos, a Super Robot Wars esc movie but with Magical Girls, a movie that Sayaka is hugely hyped about and does not disappoint when she takes Mami and Madoka on a movie date to go see it, and Tsuruno has also seen. Homura, naturally, wants nothing to do with a movie celebrating Magical Girls as a concept.
Spy x Family Project: W.E.B.: Loid finds Anya watching two in-universe cartoons which she loves. There's Spy Wars, starring Bondman and The Human Spider, starring Webman. Anya reveals to Loid that the two cartoons are going to have an In-universe Crossover.
Anya: Bondman and Webman. Together, they're going to be Web-Bond.
The Swim Of Things: Keiko, Misato and Kaji's baby daughter, absolutely loves a children tv-show called "Little People".
The 3 Little Princesses: Rosalina loves the show "Comet Academy", which comes on once every 86 years. Peach and Daisy find it utterly boring.
Rosalina: 12 Lumas are sent on the Academy Comet, which is the host of the Comet Academy! During the 86 years it takes for the comet to come back, the Lumas are training by eating the most Star Bits they can, so once in competition, they can transform into the most formidable things!
In A Very Kara Christmas, Kal's Christmas gift for his cousin is a copy of "The Kryptoniad", Krypton's greatest epic poem which Kara loves reading.
In The Vinyl and Octavia Series the protagonists get a book written about their first adventure. It's implied to be badly written.
Show is a plot point:
In Amazing Fantasy, Marvel Comics, the Marvel Cinematic Universe, and the Spider-Man Trilogy all exist in Izuku's universe, cementing Spider-Man has a purely fictional character. This is why Izuku is so bewildered when he starts developing spider powers and meets Peter Parker the same day after being bitten by a genetically-altered spider.
In Equestria: A History Revealed, the Lemony Narrator writing the fic-essay decides to go out drinking and just copies a large block of test from a book on a soldier's recounting of a significant battle in the history of the Equestrian Civil War into the fic. Notable in that the copied text proves to be vastly different in tone than the rest of the tone of the fic, probably due to its In-Universe copied nature, and is even written in a more high quality fashion than the rest of the essay-fic.
Friendship is Optimal: The plot entirely revolves around the fictional videogame Equestria Online, an MMO tie in to My Little Pony: Friendship Is Magic created at the height of it's popularity. Focus is shared between the game's developers, players, sellers, and the mysterious AI contained within.
Guys Being Dudes: My Edgelord Phase Summoned The Demon King Who Made Me His Boyfriend, the movie Spark and Arlo watch at the park as part of their celebration of Spark's birthday.
Hands (OMORI): Basil and his grandmother are shown watching mystery dramas. They teach Basil things like not going out at night, muggers like to hide in alleyways, and what rape is.
In Let Us Be Your Poison, Violet and Daisy is a propaganda-based kid's Edutainment Show featuring puppets teaching kid's how to be virtuous. It runs on Atlas' state television. Each episode ends in the duo singing about respecting family. Weiss and her brother Whitley used to watch it as kids.
Mega Man X Revenge: The titular cartridge actually has a story and isn't just some cursed game like most creepypastas. The premise being a virus known as SCP-616B infected the world with Zero killing everybody at HQ and infecting X with the virus. X has to fight and defeat those infected before he succumbs to the virus himself. Of course, the game is still dangerous. After losing five lives the game warns Ivan not to get game over or he would suffer the same fate as X.
Miraculous! Rewrite: Like in the original show, the chapter "Animaestro" is centered around the main characters going to the premiere of a movie based around Ladybug and Chat Noir's adventures. However, the movie is received negatively for various reasons, which isn't helped by the fact that the director dismisses any legitimate criticism as pointless nitpicking of his "masterpiece".
In Un-Minority Report, it's explained that famous fictional director Christopher Zillwell made a Minority Report remake in-universe in the 33rd century, which causes someone to create a machine predicting future crimes. Jenny watches the first half of the remake to get an idea of what is going on, while the cops she is working with are already fans of the film (ruining their work with that defictionalized machine aside).
The Herald and Her Knight: Ariane Yeong used to read Die Musen, a serial about a hapless painter who got swept up in the deadly intrigues of the Imperial court. The chapters of the fic are frequently prefaced with excerpts from Die Musen, with Emil the painter's situation often foreshadowing or paralleling whatever trials and tribulations Ariane and Elster are about to experience.
Son of the Sannin: An omake at the end of Chapter 68 reveals that there's a shonen series named Haruto which has pretty much the same premise as canon Naruto as we know it (and to the story itself). Itachi uses Tsukuyomi on an Amegakure shinobi he captured to torture him for information, by forcing him to watchthe entire filler season. Doubles also as a Take That! as Itachi describes said season as "72 hours of mediocre writing, forgettable characters, cheap animation and nonsensical yet predictable plots".
Sonic: Evil Reborn Zero: Atom the Porcupine doesn't end there. It's noted that the series was once extremely popular and rivaled another great franchise, but has gone through an Audience-Alienating Era filled with an unneeded surplus of characters and pitiful 3D games and, though getting back on its feet in recent days, is still ridiculed as a "kiddy game series."
: In chapters 33-40, Starscream, Skywarp, Thundercracker, Sunstorm, Metalhawk and Pharma put on a kabuki-style play called "The Matchmaker".