God-Created Canon Foreigner

Occasionally you have a character designed by the creator, but for whatever reason, isn't included in the original work, but instead turns up in an adaptation of the original work. This can at times make the fan task of establishing canon difficult. The character might not fit in the old chronology, but the Word of God implies they have a sort of elevated 'legitimacy'. Mostly though, this is a case of the creator feeling they had a good idea after their work was released, and finding a new chance to use it.

Compare with Canon Immigrant, where the original character is made by someone else.

Anime and Manga

 * Love Hina has several filler characters who don't appear in the original manga, but as they were created by the original author and don't technically conflict with the existing story, are treated as canonical. The best example is Naru's stepsister Mei, who appeared only in the manga's final chapter, well after the television series ended. (Interestingly, a seemingly identical Mei appears in Mahou Sensei Negima, causing fans to wonder if its a coincidental design holdover or an actual cameo.)
 * One major reason some fans accept Dragon Ball GT as canonical is due to Toriyama creating many of its characters before he split from the project.
 * Of course, that gets deflated a bit when you realize that Toriyama came back to Dragonball specifically because GT was such utter garbage he felt obligated to undo the damage himself.
 * That and Dragonball GT is officially not canon by Toriyama; Dragonball Online, the MMO, is the canon sequel to DBZ.
 * Contested, given that if you compare events between the manga and anime to Dragonball Online, it's easy to spot various inconsistencies: The Yardrats, characters invented for the anime, having their appearances changed for DBO; the main character essentially appearing in events that involve Son Goku and Nappa, among many others, and even battling and defeating Recoome at one point; humans having the potential to become Super Saiyans with no rational explanation other than for gameplay convenience; and the most obvious being the odd power level consistencies (Krillin being stronger than Goku during the final Tournament arc of Dragonball) scattered throughout the game. Calling DBO "canon" by any standard other than Toriyama having spent time drawing the characters (as he did with GT) is a big stretch.
 * Likewise again, the Dragon Ball anime had a movie/special about Bardock, Goku and Raditz's otherwise undescribed father, and Akira Toriyama liked him so he ended up getting a short appearance near the end of the manga.
 * Hiromu Arakawa, creator of the Fullmetal Alchemist manga, was consulted heavily for the 2003 anime version, which but eventually developed a completely different plot from the source material.
 * The second anime, Fullmetal Alchemist: Brotherhood, was a faithful adaptation of the manga--more or less. Its first episode concerned Isaac McDougall, the Freezing Alchemist--a character created specifically for that episode. He was designed by Arakawa.
 * Inuyasha in its anime form has Ayame, the love interest for Koga, who is absent from the manga. Series creator Rumiko Takahashi is so fond of Ayame, however, that she reportedly considered incorporating the character into the manga anyway. She never did, though.
 * There's also the details concerning Inuyasha's birth in the third movie: which while not based on anything in the manga, the script was written by Rumiko Takahashi.
 * Likewise, the anime adaptation of Bleach features the three modsouls that only appear in the anime from the Bount arc onwards; however, it's rumored that creator Kubo Tite likewise is considering adding the characters to the manga.
 * Another example is Ashido, a shinigami living in Hueco Mundo whose appearance was cut from the manga for timing issues, then added in the anime.
 * The story of the Bleach game The 3rd Phantom can be considered semi-canon because it's written by Tite Kubo himself.
 * The recent "Zanpakutō Unknown Tales" arc features the true forms of some of the main character's swords - the designs of which were made by Kubo himself. In a recent interview, he stated that he would have liked to add the Zanpakutō spirits into the manga, but didn't have time.
 * The Zatch Bell manga began with Kiyo discovering Zatch's powers; they didn't meet a "mamodo" team until the next chapter. The anime stuffed what many fans believed to be a non-canonical mamodo team in the first episode, Hyde and Eido. This was reinforced by the plot point that everyone's spellbooks would tell its owners how many mamodo were left in the battle, something not shown in the anime. However,
 * The second season of the Magic Knight Rayearth anime features two villains not found in the manga, Nova and Lady Debonair, who were designed by CLAMP for the anime. Lady Debonair even makes an appearance (under a different name) in the Tsubasa manga.
 * In the first animated adaptation of Guyver, Oswald Lisker -- Guyver 2 -- was replaced by a female version, Inspector Valcuria, designed by the original author. Recently, she's shown up in the manga as a new Guyver looking just like her animated incarnation.
 * Eiichiro Oda is behind the writing and character design of the tenth One Piece movie One Piece Film Strong World, which features as its antagonist the "Gold Lion" Shiki. Shiki was recently referred to in the manga as the only person in recent history to ever escape One Piece's Alcatraz Impel Down. In the art book for the movie Oda actually does state that Strong World is canon for both the anime and manga.
 * Other characters that are God Created Canon Foreigners include Musshuru (9th movie), Don Achino (Ice Hunters filler arc), and Daddy Masterson (Loguetown filler). The latter was actually supposed to appear in the manga, but was cut because Oda wanted to reach the Grand Line on the 100th issue.
 * Rebuild of Evangelion is being made by almost the same team that created the classic series. So it's not surprising that newcomer Mari Makinami was designed by the original character designer on behalf of the original director...
 * A dating sim game based on the Revolutionary Girl Utena anime was released on the Sega Saturn some time after the anime's release, and it is set between the first and second story arcs. Both the scenario and the game's Big Bad, Chigusa, were respectively written and conceptualized by Kunihiko Ikuhara, the director of the anime, and he himself stated that the game is, in fact, canon. Those who watch the game's scenario If for nothing else, Ikuhara's flavor is woven into the script, such as the humor and Chigusa's view on women: the innocent princess Snow White versus the Evil Queen.
 * Hajime Kanzaka, the writer of the novel series, wrote out some scenarios for the Slayers anime and also wrote the story for the Alternate Continuity Hourglass of Falces manga. The third anime season in particular is original material that he was involved with; in this case, he didn't care for the end result.
 * However, a character poll in Japan had the third-season/anime exclusive villain Valgaav in the top 10, and Kanzaka more or less acknowledges his existence along with a few others.

Film

 * Wybie was created by Neil Gaiman for the movie of Coraline. In the book, Coraline spends a lot of time on her own and most of the exposition is her internal monologue. This doesn't really work all that well in movies, so they had to give her someone to talk to, and Wybie was born.

Literature

 * J.K Rowling wrote two Defictionalised books from the Harry Potter series; Quidditch Through The Ages and Fantastic Beasts and Where to Find Them for Comic Relief. She stated that they consisted of stuff from her own notes that she would never have space to use in the books/wrote for her own amusement.
 * In Kim Newman's Anno Dracula series, one of the major recurring characters, journalist Kate Reed, is a character originally created by Bram Stoker in early drafts of Dracula but removed from the published version.

Live Action TV

 * While Damon Lindelof and Carlton Cuse have been clear regarding the fact that the Lost video game, "Via Domus," is non-canon, some elements of the game were created by the pair and were originally intended to be in the show before being thrown into the game instead. However, despite this claim, some of these "official" elements have ended up conflicting with the show's later seasons. The biggest example is the "Incident Room," the room behind the concrete wall in the hatch. The room was intended to be shown in the series but wasn't, and the design was given to the developers to be used in the game.
 * However, this room ended up conflicting with the show's portrayal of the actual "Incident." In the game, the room contains a large, busted generator with electricity flowing through it, implying the "Incident" was some sort of electromagnetic generator failure. However, the show's portrayal of the "Incident" was much different: it occurred while, involved , and possibly . No room or generator was involved.
 * In the 2008's adaptation of La Dame de Monsoreau Joyeuse make an apparition. He is one of Henri III's favorites, on Les Quarante Cinq, a novel that takes place 7 years later than the events depicted by La Dame de Monsoreau.

Radio

 * Douglas Adams always added things and changed continuities in The Hitchhiker's Guide to the Galaxy. Since the basic work has seen light in eight media -- radio drama (which came first), LPs, novels, stage productions (which introduced the dish of the day), TV series (which added the food on the Vogon ship, and the important detail that Arthur had been wearing his bathrobe the whole time), video games (which added lots of backstory and the Catch Phrase "Show No Tea to the door"), a comic, and a film -- this example is particularly famous. Although the film was made after his death, most of the plot-altering elements added to the film (the Point-of-View gun, the little things that pop up whenever you have an idea on the Vogon homeworld, etc.) were thought up by Adams himself.

Toys

 * Born Of Plastic? In Transformers fandom, this manages to mix with the Merchandise-Driven nature of the franchise to form an extreme case... even if a character doesn't have so much as a cameo anywhere in the Expanded Universe, if a toy is made, it's implied that that character is out there somewhere. Not that Doom-Lock or Hardtop will ever drop us a line or anything, but we know they're somewhere doing their thing.
 * For instance, in 2006, seven years after Beast Wars ended, a comic came out showing what all the characters who were in the Beast Wars toy line but never showed up in the show were doing.
 * Also, with the number of Promoted Fanboys involved with TF production, never count out any of them when it comes to getting their day in the sun. Doom-Lock was scheduled to appear in the Transformers Energon comic, but Dreamwave went kaput before he could. Hardtop has since appeared in some comics and one text story. The IDW Comics series, on the other hand, has a gazillion characters of varying importance who have been toy-only - since 1985.
 * Speaking of Hasbro toy lines, there are over 50 Generation 4 My Little Pony characters who aren't in Friendship is Magic. Only one of them, Blossomforth, has gone on to appear in the show.

Video Games

 * Akaii Ringo of the Tokyo Mew Mew Playstation game was designed by Ikumi Mia to fulfill the RPG convention of a healer, which helped cement her in the fandom. Unfortunately, many non-players ended up using her as a Possession Sue.
 * The Updated Rerelease of Persona 4 features the character Mary.
 * Katawa Shoujo has Saki Enomoto and Rika Katayama, two "DLC love interests" announced as an April Fools' prank by the development team, with mock screenshots and personality profiles. Ultimately, they were never even mentioned in the final game, but they became Ensemble Dark Horses anyway.

Western Animation

 * Disney's Max Goof. Most Disney characters in formal canon have film legacies and iconic Vague Age personalities. In contrast, Max is a Canon Immigrant whose age is usually explicit Depending on the Writer, but appearing in Goof Troop, several Disney direct-to-video films, and A Goofy Movie and its sequel has given him some added sense of legitimacy.
 * Several characters developed for Teenage Mutant Ninja Turtles 1987, such as Bebop and Rocksteady, were originally designed by Turtles creators Eastman and Laird. Ironically, this was not enough to grant the characters Canon Immigrant status, and Peter Laird, in particular, was adamant about not including them in adaptations he was involved in.