Bakuman。, being a manga about writing manga, has tons of these, with the majority of the cast involving themselves in at least two works. The manga focuses more on the characters' lives than on what's happening in their stories, but gives us occasional glimpses of pages from the characters' series. On one occasion, a special chapter of Bakuman was a chapter of an in-universe manga, Otters 11. There's also even briefer glimpses at the anime roles Mashiro's fiancee Azuki plays, but in most cases, the viewer is lucky to see their titles.
Billy Bat has a comic of the same name within itself, and it's actually not until halfway through chapter two that we find out the comic itself isn't the real story.
One of the extras from Black Butler involves the cast putting on a production of Hamlet as a charity event for children. At least that is the play they intended to perform.
This is unavoidable for The Comic Artist and his Assistants, as it is basically about a Sequential Artist. Aito works on Hajiratte Cafe Latte, which basically runs his Author Appeal of panty shots, Tsurameki has Hot-Blooded Fighter(which was Cut Short), Meisei has JOD: Judge of Darkness, Tamako has Tension 1000%, and Ichika's Adventure World. On the other hand, Aito follows an anime called Magical Girl Momoko-chan, clearly a spoof of the many seinen demographic magical girl anime in the 2000s/2010s.
In the last episode of Mangirl, they create an anime about the main characters making a manga magazine. It's identical to Mangirl! in every way. The ending merges the OP with a scene of the characters watching exactly the same OP. Whoa.
Comic Girls is similarly about a group of 5 highg-school age female manga artists sharing a dorm. Our protagonist does Yonkoma, the other residents do Horror, Shoujo, Shōnen, and Teens Love comics, with the latter two being in syndicated publiction.
From Cromartie High School we are introduced to Pootan, a show that makes less sense than the characters who watch it.
A manga chapter reveals Nobita to be a fanboy of a Magical Girl show and excitedly discusses about it with Shizuka and the other girls in his class, leading to Gian and Suneo teasing him about it.
Gintaman in Gintama, a self-parody within the story. Also Oshiete Gin-pachi Sensei and Kintama at the start and end of the regular episodes in different seasons.
Gundam 00: A Wakening of the Trailblazer has Celestial Being: The Movie, a film based on the publicly-known exploits of the namesake group in years past. However, it is par for the course grossly inaccurate, for featuring a number of anime and Hollywood cliches and over-exaggerating the characters of the story. They even brought out someone who was already dead midway into the original story and used him as the over-the-top, equally-hammy main villain.
At the end of some episodes of SD Gundam Force is a Zako Zako Hour, a lecture hosted by three Zako Soldiers to other Zako Soldiers. These lectures act to give background information on certain aspects of the main series, like why the Dark axis uses Control Horns among other things. Each show normally takes place on a stage in the Dark Axis ship Mangamusai, even after it was converted into the Gundamusai.
Haru wo Daiteita has the two main characters making a movie that actually gets spun off into its over OVA series called Winter Cicada.
HeartCatch Pretty Cure! has Tsubomi and Erika discover the banchou-type character Ban is making manga. Manga of them. They give him a hand in completing the pages he'd drawn and help him finish the story he was stuck on by acting out an ending. Ban's afraid to reveal this to his mother, who grew up without manga and felt that if she knew, she'd hate him.
Lucky Star's Lucky Channel. One male character shows up as one of the two characters in the show main, something that gets Lampshaded to all pain by his co-host (who doesn't get that luxury). Lucky Star and Lucky Channel are Mutually Fictional, judging by its appearance in the final episode.
Lucky Channel is also the name of the reader's column in the magazine Lucky Star serializes on.
Episode 10 of Macross Frontier features the cast involved in the filming of "Bird Human", an in-universe retelling of the events of Macross Zero.
Metamorphosis 2013: ShindoL released a page of bonus material on his Patreon which reveals that Metamorphosis is a fictional movie in-universe. Saki's actress arrives on-set wearing a ShindoL boggin cap, is shown putting on makeup, and takes direction on her expression during a sex scene. She also tries to do a coke-snorting scene but it goes badly, and Hayato's actor asks if she's okay.
In episode 10 of the anime of Miss Kobayashi's Dragon Maid, the dragons put on a Christmas play for the residents of the local retirement home. The play starts with The Little Match Girl, but the plot soon goes off the rails. In spite of this, the audience likes the play.
In Monster, Bonaparta's son writes and performs a puppet show that parallels the events that are actually happening, but of which does not actually know anything. Also, Grimmer loved the show Magnificent Steiner when he was a kid. He never saw the last episode, though.
Monthly Girls' Nozaki-kun is an Affectionate Parody of shoujo manga and its making, so naturally there are quite a few examples. The most prominent is Let's Fall in Love!, the shoujo manga that Nozaki himself writes and draws.
In Naruto "Specials," and at the end of some episodes, the characters are portrayed to be narrating their own show.
Jiraiya's novels: "Icha Icha Tactics" was used as a codex, while "Tales of a Gutsy Ninja" is Naruto's namesake. Also the hero is an amalgam of Jiraiya and Nagato.
Also, the Princess Gale movies from the first movie and background elements of the anime.
Nurse Witch Komugi redefines its parent series The SoulTaker as a live-action drama by bringing the cast back as actors and following their lives behind the camera in a massive tone-shift from the original series.
In Prétear, Sasame is the host of a radio talk show called Sasame's Words Gate, in which he gives listeners advice about their problems they send in on anonymous postcards. Himeno's step-sister Mawata is a fan of the show and frequently sends in her own postcards — which becomes a major plot point, particularly in the anime.
Sakura Wars's variousadaptations are loaded with these, because of the entire cast's cover identities as part of a theater troupe. In addition to the many, many stage productions they put on, there are also the movies made by the studios owned by Sumire's family (including the infamous Crimson Lizard), and the radio serial Red Lad.
In what is likely a Shout-Out to Lucky Star, a few episodes of Sayonara, Zetsubou-Sensei have the characters taking comments from viewers and behaving like actors/tv presenters. In one instance, it's referred to as "Zetsubou Channel".
The anime that the girls from Seiyu's Life! are voices on is Buddha Fighter Bodhisattvon, which, going by the logo, is a reference to Evangelion.
Shirobako is about five girls and their experiences as they work at an animation studio, so naturally there are several examples. The two in-universe anime that get the most focus are Exodus (an original anime) and Third Aerial Girls' Squad (which is adapted from a manga), and how the characters work on both series. There's also Aoi's favorite anime, Andes Chucky, which is inspired by the World Masterpiece Theater anime Rocky Chuck the Mountain Rat; it's later revealed that most of Musashino Animation's older staff worked on it.
Star Driver had "The Eve of the Legend", a play put on by the main characters near the end of the show. Its themes heavily parallel the main story and it is hinted to be a (allegorical) backstory on the the Cybodies themselves. It turns out that the club's president, and writer of the play, is a Human Alien whose race was involved in the Cybodies in times past, who likely did this on purpose. For further meta points, the play is also a prequel to a story that was told earlier in the show by "Sakana-chan" to the leader of the Glittering Crux, which also parallels the main plot!
Most of the main characters in Sweet Blue Flowers are in their school's drama club, and stage plays for the culture festivals, the ones who aren't in the club help out anyway.
Tiger & Bunny has HeroTV, a combination news-Reality TV show that focuses on the exploits of Sternbild's various corporate-sponsored superheroes.
Tokyo Mew Mew has Only One Wish, a miniseries featuring Zakuro as the "Angel of Wishes" (a mysterious entity that grants wishes of those who can contact her and either screws them over or grants them better than the wisher could have expected... And Ichigo as the Angel's cat. In an unusual development, Only One Wish is actually a different manga from the same author, and we only know that it's this trope for TMM from the volume edition showing Zakuro being hired for the show and getting Ichigo to play the cat.
To Love Ru: Magical Kyouko, a show about a magical girl with fire powers. Except Kyouko is actually a half human/half alien with real fire powers when the cast meets her for real. Run has a reoccurring guest role on her show.
Tsurupika Hagemaru-kun has this. Ever seen the best of 10?
Waiting in the Summer is based around the extremely amateur movie the main characters are working on. It also has some elements of Plot Parallel (Ichika is a recently-arrived alien in both).
In Yu-Gi-Oh! ZEXAL, there is D.D. ESPer Robin (The Sparrow in the dub), a live-action television science fiction series. The show's star is Fuya Okudaira, who becomes a minor antagonist after falling under the control of a Number (causing him to believe he literally is the heroic character he portrays on the show). His deck as a duelist uses cards that resemble characters on the show, most likely custom-made.
Sokosoko V, Ditzy Tiger, as well as a Magical Girl series, in Yutori-Chan. The cast works at an office that's responsible for promoting these series, and commercials for these meta-franchises show up at the start of every episode.
Characters are fans
The titular character of Crayon Shin-chan loves to watch Action Kamen. Some episodes of the series are dedicated to him, only showing his adventures, and then they show Shin-chan laughing like Action Kamen while watching the episode on TV.
In the gag dub, it is called Action Bastard
He also likes to watch Quantum Robot
Bamboo Blade's Tama is a fan of the toku show Chouken Sentai Blade Braver. Another show called Materia Puzzle also makes a short appearance.
The Dangers in My Heart has Kimi-Iro Octave, a shoujo romance manga that Yamada and later Ichikawa read. What's seen in the series is used in moments that parallel Ichikawa and Yamada's growing relationship. The female lead is an identical clone of Yamada and the male lead Nigorikawa shares a significant number of Ichikawa’s personality traits (Which he subconsciously denies). Nigorikawa himself eventually manifests within Ichikawa's mind as a psychological representation of his growing self-esteem and true desires.
Fruits Basket has Mogeta, a popular children's manga and anime which seems to be about a boy and his Cartoon Creature sidekick Mogeta who go around fighting various monsters and villains. Kisa is particularly fond of the series and is sometimes shown watching the anime with Hiro. There are other nods to it throughout the story as well; Kyo, Yuki, Tohru and Kagura go on a Double Date to one of the movies, various characters are occasionally seen reading volumes of the manga, and Yuki goes out of his way to buy Machi a Mogeta paperweight and later a soft toy.
Genshiken has Kujibiki Unbalance, a manga/anime that the members of Genshiken are obsessed with despite being a (deliberately) blatant Cliché Storm of tropes that were popular in manga and anime at the time. Despite its heavily tropey nature, it became popular enough in real life that it was soon spun off into its own series.
Hand Maid May has an incredibly cheesy and overdone soap opera.
Kaguya-sama: Love Is War has Today Will Be Sweet, an angsty, Glurgey shoujo manga which the main characters become obsessed with.
The fictional anime series Liddo-kun no Daibouken (and the stuffed Liddo-kun toy owned by Naru) figures significantly into Love Hina.
Detective Kunkun within Rozen Maiden (may actually fall into the "eerily similar" category in some respects, as it's a puppet-based show watched by the Rozen Maiden dolls, who are convinced it is reality). The irony of the characters watching a dark and edgy cartoon involving dolls does not go unnoticed.
School Rumble has The Three Slashed and Hatenkou Robo Dojibiron.
The unnamed alien Soap Opera that most of the Masaki household watches at one time or another in Tenchi Muyo!
Welcome to the NHK's anime adaptation has Puru Puru Pururin, a Magical Girl anime which Yamazaki is a huge fan of and Satou believes to be the forefront of a conspiracy (in the original novel, Yamazaki's obsessed with the real anime Ojamajo Doremi instead). Despite its show-within-a-show nature, a real OP was made for it and it once had a real website which is now defunct.
Sensei and Ninomiya-kun, the soap opera that the Minami sisters watch in Minami-ke.
In Penguin Musume Heart, Sakura is a fangirl of the Sunday morning Magical Girl show Takenoko-chan. That Kujira looks like the main character is partially responsible for Sakura starting her crazy antics.
Takumi of Chaos;Head is a fan of the show Blood Tune. It appears to be some type of Magical Girl show — or at least a moe one, given the sheer amount of figures he has of lead character Seira. Creepier, though, is that he's deluded enough to see Seira in his room and talking to him.
Princess Tutu: In two different episodes the school puts on a ballet and a dramatic play, each mimicking the plot & themes of those particular episodes.
The story of The Prince and The Raven guides the characters both thematically and, in some cases, literally. It exists as both a living narrative and an actual novel that various characters read.
Hidamari Sketch has Fashionable Detective Lovely Chocolat in its anime version.
In Codename: Sailor V, Minako is obsessed with a manga and anime called Aurora Wedding, which is about a group of Magical Girls who run a bridal shop. Though we never get a good look at the women, it's clear from their hairstyles that they look exactly (at least in silhouette) like the main characters of Sailor Moon.
Sailor Moon features the Sailor V franchise, which started out as a video game Artemis came up with to train Minako in Codename: Sailor V. The kicker is that Sailor V is a real person, but apparently has shows and merchandising anyway that she clearly has nothing to do with. The show itself is never seen, but an episode of season 1 of The '90sSailor Moon features the production studio for Sailor V and was an excuse for the Sailor Moon animation studio making fun of themselves. We later see evidence — a plush doll of Sailor Moon herself — that similar exploitation of the Senshi is taking place.
This is subverted and parodied in the live action Pretty Guardian Sailor Moon, where Minako (Sailor V) is a recording superstar and media juggernaut who apparently creates all her own promotional campaigns. Minako's current hit song in the series is "C'est La Vie", which is phonetically identical to "Sailor V" in Japanese. It comes off an album entitled "Venus", and includes lines like "As long as I am me, C'est la vie". Another song off the same album is named "Venus Over My Shoulder".
Cowboy Bebop has Big Shot!, a TV show which features information for bounty hunters on the latest rewards posted for the capture of criminals. One of the hosts of the show is seen in the background at a spaceport late in the series (though the main characters don't notice him).
Nodame Cantabile has Puri Gorota, a children's anime similar to Doraemon which Nodame is a huge fan of, to the point of collecting figures of it. One teacher uses her love of the show to bring her to the classes she kept missing. Nodame uses it as example to teach Chiaki a lesson. In Paris, Frank was trying to record the French dub of the show when Nodame notices it and watches one episode several dozens of times in order to learn French.
Most of the real kids in Case Closed are fans of Kamen Yaiba, a Lawyer-Friendly Cameo version of Kamen Rider (which takes the name "Yaiba" from another of the Conan mangaka's works). A number of times, Conan & company solve mysteries at sets, stunt shows, production offices, or production studios associated with the franchise (and in one case at a costume party where cosplayers showed up in intricate Kamen Yaiba outfits).
In Pokémon Adventures, Diamond is a massive fan of Proteam Omega, an anime featuring the superhero adventures of a Combining Mecha. Diamond sings the theme song to bolster his spirits whenever he's afraid, and the show in fact is one of the reasons he decides to fight Team Galactic. The Goldenrod City Radio Director made the show by basing the mecha off of Red's team. Silver, adorably enough, is also a massive fan.
Helvetica Standard, a manga/show that is much, much weirder than is already implied by being named after a typeface, within Nichijou. It mostly pops up randomly as an intermission, but characters are seen reading Helvetica mangas occasionally.
The Kurosagi Corpse Delivery Service has Magical Maid Girl Mumume-tan, whose lead character Makino sometimes professionally performs as in personal appearances.
Kae from Kiss Him, Not Me is a fan of Katchu Ranbu, which is very obviously based on Touken Ranbu (being about anthropomorphic armor instead of swords).
Itami is a fan of several magical girl manga and anime, including one called Mei Company, which was later turned into a real manga.
Risa is a mangaka who specializes in yaoi works. Princess Piña and many of her knights become fans of them.
The protagonists of SKET Dance are fans of an anime called "Futari wa Nervous", which is obviously a parody of Futari wa Pretty Cure. The protagonists are an engaged woman and a pregnant woman, and centers on how the two protagonists manage to defeat the mysterious villain despite their many personal anxieties.
Yo-kai Watch has Space Wars, which Nate is a fan of. His favorite character is "Mr. Epockman", a parody of Darth Vader.
Meanwhile, Hailey loves Pretty Guardian Sailor Piers, and, when she goes to buy an action figurine, she ends up buying a Yo-kai Watch U Prototype, kickstarting her encounter with Yo-kai. On that matter, upon meeting Usapyon, he pulls a volume of DeDeDe no Detaro in order to figure out what he is.
And let's not forget Jibanyan's love for NyaKB (known as Next Harmeowny in the dub). It became full circle when the group formed in real life with members of some units from AKB48 and composed the third ending of the anime.
In Shy, the titular heroine gets roped into cosplaying the main character of the Magical Girls anime "Rise! Civil Revolution" and becomes an instant fan of the show.
Teasing Master Takagi-san: In the spinoff Karakai Jōzu no (Moto) Takagi-san, which features Takagi as an adult raising her daughter Chi, one of the author's other works, In the Heart of Kunoichi Tsubaki is a television show enjoyed by Chi. This is shown in Tsubaki in an omake in volume 6, while chapter 208 of (Moto) has Chi's mimicking the ninjutsu she sees on TV getting out of hand.
Anya from Spy X Family is a big fan of the in-universe cartoon Spy Wars, particularly of its main character Bondman.
Show is plot point
In (Zoku) Sayonara, Zetsubou-Sensei episode 3, we see Harumi undergo the process of drawing heryaoi doujin one summer night while listening to a radio show with the other characters talking about acting their age. These are two separate stories, though they occasionally overlap with cut shots and her comments. The radio show is the actual adaptation of the manga chapter, while the night in the life of Harumi is anime-specific.
Kirby: Right Back at Ya! features its own television channel. Said channel generally only contains shows made by King Dedede himself, and is often used to start off or elaborate the plot.
Dedede took a shot at adding cartoons to his channel. Shows made include Dedede: Comin' at Ya!, an anime where Dedede trades roles with Kirby, but which fell victim to half-assed animation and odd dubbing (while Meta Knight found the script too ridiculous to finish) and The Tiff Show which was made by a trio of "professional" animators featuring an aged-up Tiff. She was not pleased.
Chobits: A City Without People is a series of picture books written and drawn by Chitose Hibiya, the wife of Chi's original creator, which Chi buys and becomes more intrigued by as the story goes on. The books' story hangs a lampshade on the problems Persocoms are causing and drops hints about Chi's true nature and eventual internal struggle.
In Servant × Service, there is Magical Flowers, a Magical Girl series which bears more than a few similarities to Heart Catch Pretty Cure. Its five protagonists' color schemes also bring to mind Puella Magi Madoka Magica, while one of them, Rose Black, looks like a recolored and redesigned Blue Rose. However, its use seems to only allow the local Cosplay Otaku Girl Chihaya something to cosplay on; most of the young-adult cast don't even know what it is.
The Geek Ex-Hitman: The entire plot of the series is kicked off when Italian mafiahitman Marco catches his latest mark in the middle of watching a Magical Girl anime called Hades Girl Eurydice and becomes obsessed with the series himself: he leaves the murder business on the spot and moves to Japan, pursued by two Carabinieri, Viviana and Andre, who come to be fans themselves once they're convinced he has no intention of returning to organized crime. The anime seems to be a pretty big deal in the manga's version of Earth: there's even a movie and soundtrack concerts, and Marco, Viviana, and Andre are able to sell a doujinshi of the series that they make.
Haruhi Suzumiya: The Adventures of Mikuru Asahina, the Non-Indicative First Episode of the anime adaptation (sort of), which is produced by the main characters, foreshadows the weird goings on (most notably the existence of aliens, time travelers, and espers) that are the focus of the rest of the series.
A chapter of Assassination Classroom revolves around several of the characters going to see "Sonic Ninja," an American superhero movie. The major connection comes when the film's Big Bad is revealed to be the heroine's brother, which serves as Foreshadowing for the eventual revelation that the next assassin to come after Koro-Sensei is his younger brother.
In Neon Genesis Evangelion there are frequently radio and TV talk shows subtly playing in the background that mirror psychological issues being dealt with in the show. Especially prevalent in the first half of the show.
Yes! Pretty Cure 5 has a variation, in which Urara plays a character on an as-yet-unnamed TV show. By all indications, said show appears to be essentially a live-action version of... Futari wa Pretty Cure Splash★Star, the previous Pretty Cure series.
Just to make things more complicated, a question on an English test seen in an episode of Splash Star suggests that that series has the original Futari wa Pretty Cure as a show-within-a-show. Although it's probably just an Easter Egg, a number of fans have taken both of these as gospel and sincerely hope that this trend continues with later Pretty Cure shows.
Some of Mamoru's classmates in GaoGaiGar are fans of a show called GaGaGatchi, which stars a little gnome robot who bears suspicious similarities to GGG himself. When Sixth Ranger King J-Der shows up, he gets his own GaGaGatchi expy in the form of The Rival "King Snow".
Admiral Geroro in Sgt. Frog, although Geroro sounds as though he has more luck than Keroro.
In the universe of Digimon Tamers, "Digimon" is a popular franchise, with it's own TV show. The cards, specifically, were very useful. The original Japanese version of the anime does not specifically go into any details about the TV show, but Word of God (delivered via the head writer's website) certainly implies that it is the previous two series of the real-life franchise, collectively known as DigimonAdventure. The English dub of the series made this fact explicit, as did later Japanese media like Digimon Fusion.
Kirby: Right Back at Ya! has done this a few times. One is when King Dedede convinces everyone in Cappy Town to get him his own anime series. Since nobody has had any professional training, and each animator has a different style, it comes out looking shoddy and inconsistent (in one case, Dedede and Escargoon are drawn hyper-realistically). Since Kirby is just a baby, his scenes are just scribbles. Another is when Dedede creates his own TV channel that he uses to convince people that Kirby is evil. There's also the Otakings' anime featuring Bouncy Tiff...
In Saint Beast the Poison Saint show plays on Earth, which has Super-Deformed versions of the characters doing things that just happened in the show. The actual characters fail to acknowledge it's about them even despite the fact one of them watches it avidly.
In chapter 37 of the Omamori Himari manga, there's a single panel showing Yuuto playing a video game of Himari fighting Shizuku.
Taken to MindScrewy heights in Satoshi Kon's Perfect Blue, where the internal show's plot seems to mirror reality so impossibly well that the line becomes impossible to find. There's a part at the height of the confusion where there's a sequence of scenes which all look like they're about the main character's real life struggles, including a scene where she's declared to have multiple personality disorder and to falsely believe she's an actress, only for someone to yell "Cut!", several times (while she's suffering identity crises of her own thanks to her stalker/impostor). The viewer is left questioning whether that really was just part of the show. The show also pushes itself onto reality with the rape scene, which Mima tries to play off as no big deal except as a boost to her career but in reality took very hard).
Similarly played with (but mostly without the horror aspect) in another of Satoshi Kon's movies, Millennium Actress. The movie depicts the life of a retired actress through a series of long flashbacks, which are intertwined with scenes from her movies. This being a Satoshi Kon movie, it's rarely entirely clear what's from a movie and what was her actual life. Either she was typecast in a ludicrously specific role, which happened to very closely mirror her actual life, or...
The first episode of Mobile Suit Gundam Unicorn features an advertisement for a film called "Runaway Princess." Guess what the plot of the series revolves around?
Persona 4: The Animation revolves around a group of high school kids as they try to solve a series of bizarre serial killings in their town. As a plot parallel, the main protagonist's younger cousin is obsessed with Magical Detective Loveline, a fictional Magical Girl anime about a teen detective.
Phantasy Star Online 2: The Animation is a wonderfully Mind Screw version of this trope. The main characters are fans of and play the video game Phantasy Star Online 2. At first, things seem like it's about adventures of the characters playing the game, however it's revealed that they're actually going into the game, part of a plot by an evil organization peering into the actions of ARKS in that universe. This is actually a StealthPrequel to the actual video game's EPISODE FOUR storyline, which has the Player Character and Matoi awakened from cryo-sleep to find out what the hell is going on.
Examples of multiple types at once
In Ah... and Mm... Are All She Says, Norush is a fan of the Magical Girl anime Star Divine City Luck and Sister (or "Luckysis" for short), and introduces Toda and Tanaka to it, who become fans as well. Norush, Toda, and several other mangaka then make a doujinshi of it to sell at Comike. Not to mention all the hentai manga the characters draw for the magazine (for example, Norush's Senpai, Kouhai, Doggy Style and Toda's Ashen Oil), though most of those are oneshots.
Hozuki's Coolheadedness have the widely popular anime ChineseAngel . Severals characters are fans of the show and the it is often talked about. Also it is first mentioned when Peach Maki is cast to play the role of one character in a live event.
One of the allies of Part 4, Rohan Kishibe, is a manga artist for a fictional series called Pink Dark Boy that runs in Shonen Jump.
Koichi and Hazamada are fans, and Koichi's introduction in The Movie shows him in his room amongst Pink Dark Boy posters and volumes of manga.
Rohan often agrees to do things and go places if he thinks the real-world experience will benefit the creation of his manga, as he believes real-world experience makes a person's writing more believable, a belief echoed by Hirohiko Araki, the author of JJBA.
Finally, his Stand, Heaven's Door (who is a dead ringer for Pink Dark Boy), allows him to turn others' minds into a book, and at least early on, wasn't against actually ripping pages out of their minds and using them as basis for characters in his manga, causing weight loss and mild amnesia to the victim.
Kiss Him, Not Me gives us Mirage Saga, a high fantasy shounen anime, being the sole reason behind Shiranuma's despair-induced weight loss and her refraining from talking to one of the boys due to his resembling her favorite (dead) character.
Nadesico. The characters are fans of the show and watch it quite frequently. But fandom of Gekiganger 3 becomes a fairly large plot point. And at its less serious moments, the events of the show mirror what happens in the Nadesico episode. One has to imagine the writers had a lot of fun with this trope.
By popular demand, they produced The Movie of Gekiganger 3, by incorporating recycled footage from the Nadesico tv show and new segments, and released it as an OVA. It is framed by the scenes of Nadesico characters who go to the cinemas to watch the movie, naturally.
The Creators of the various media the Creations come from are main characters, and continue to work on them during the plot. Later on, the Creators and Creations make a show within a show of their own together.
Multiple characters are shown to be fans of the Creations' home series. Setsuna was a fan of all of them, which is why Altair brought characters from those specific series to the real world.
The Elimination Chamber Festival was made specifically to trap Altair in a work of fiction so she would have to adhere to the rules of it. Unfortunately, the plan backfires spectacularly.
The Tamagotchi television series features a superhero show within a show called Gotchiman. Mametchi is a big fan of it and Lovelitchi a.k.a. the Idol Singer Lovelin plays Gotchiman's sidekick in the show.
Tenchi in Tokyo In the former, Mihoshi and Kiyone got jobs playing villains in the TV series, Space Police Policeman, and in the latter, Mihoshi became a big fan of the show.
The Way of the Househusband: Tatsu's wife Miku is a big fan of a police-themed Magical Girl anime called PoliCure (which is an obvious riff on Pretty Cure), which gets them into things like becoming an audience participant in a PoliCure live show, trying to get hold of limited-run merchandise, and putting on a show for a little girl in hospital who's also a fan. The anime adaptation goes one step further with Toei Animation (the creator/producer of Pretty Cure) creating an opening for the series, officially titled "Crimecatch PoliCure", which specifically references HeartCatch Pretty Cure!.
and it once had a real website which is now defunct.