- To Hell and Back (Arrowverse): The author is always happy to explain why things are happening in post-chapter notes.
Avatar: The Last Airbender/The Legend of Korra
- Better Off Not Knowing: Confirmed via the author's blog and the fic's tags: the tween viewpoint character's name is Hakini, she lives "somewhere in the Fire Nation," she's 5'11", and what looked familiar to her about the Arc Villain's mug shot (and was thus the first hint to readers that Hakini is his biological daughter) was his cheekbones.
- Vow of the King: The side story Extra Vows contains background information about the universe in which the story takes place but isn't relevant to the actual story, such as the fate of Yhwach, how the Kenpachi title came to be, and details about the Royal Guard.
- The bonus chapter for Season Two of Calvin & Hobbes: The Series reveals Andy is homeschooled, and both him and Klein are named for their (proposed) voice actors (Andrew Lawrence and Robert Klein, respectively).
Crossover
- Child of the Storm: the author frequently elaborates upon/clarifies various points as they come up at the bottom of chapters, along with an occasional sketch of what he's been up to/why this chapter is longer or shorter or later than usual. He also elaborates on details in private messages, and on various forums he frequents.
- Cycles Upon Cycles: As is tradition with Mass Effect fics, most chapters ends with one or two Codex entries relevant to the events of the chapter. Recently the Codex entries have been replaced by brief dossiers of Shepard's crew.
- Flashpoint 2: Advent Solaris (DC Animated Movie Universe & Sonic the Hedgehog): Takes place after the final movie in a series, and as such most of that film's events would require viewing said movie to read - in addition the events of any Sonic game prior to Sonic 06 is also mostly relied on the reader having either played or looked into said games, as only 06 is being directly touched on here.
- hush now, little one (Encanto & Turning Red):
- Which niece Bruno is comparing Tae-young to is unspecified in the story, but the tags confirm it was Isabela.
- Grandma's name is never said in the fic. The tags refer to her as Aera Jung.
- Infinity Train: Blossomverse has many stories that details author notes in regards to the authors' take on either Infinity Train or Pokemon: The Series, stuff that had to be removed from the story or their thoughts on characters.
- The Institute Saga (Superman & X-Men: Evolution): The art gallery includes several plot-relevant images, Chekhov's Guns and background details, such as the cross-section of the moonbase tunnels
. - Manehattan's Lone Guardian: The author posts profiles of some of the original characters on his blog at Fimfiction; these contain details about them that never come up in the story proper on account of them not being plot relevant. Metallium's profile, for example, states that she has a lazy older brother who would eventually be scared away by Fluttershy.
- Stars Above (Lucky Star & Puella Magi Madoka Magica): The true names, natures, and backstories of the Demons called the Nine are revealed almost exclusively through the Demon Profiles, written in the style of the Witch Cards from the official Madoka website.
- The Dragon Age: Inquisition series Twice Upon an Age plays with the trope. One side volume, The Skyhold Runner's Guide to Survival, is explicitly presented as a manual, and it functions as one in-universe, but the reader doesn't really gain any additional information from it; it's more of a repository for Varric's humor than anything else. By comparison, the other side volumes Across the Waking Sea and Agents Acquired do give the reader insight into details they otherwise wouldn't know.
- The Wrath of Avelina: Exactly which of the Sisters' doors Avelina tried to open is not specified in the story; only by reading the comments on Chapter 7 would a reader learn that it was specifically Sierra's door.
- For Family Guy Fanon, certain extension details for characters like Herbert's past, Randall Fargus' birthday and Stan Thompson's unhappy childhood that made him who he is are only found on their respective pages.
- Game of Touhou (A Song of Ice and Fire & Touhou Project): There is a lot of supplemental material in the author's DeviantArt page, and there are even unreleased voice-ins of every faction.
- Neither a Bird nor a Plane, it's Deku! (The DCU & My Hero Academia): The author's comments on Spacebattles and Archive of Our Own allude to things set to happen in the future or bring up details that would bog the story down. For instance, there hasn't been a major superhero team since the dissolution of the Justice Society of America.
- Sudden Contact (Mass Effect & StarCraft): The "Timeline and UED Factional Analysis" and "Terran Codex" both provide supplemental materials for the main stories, providing the UED's anaylsis and opinions on both the Koprulu and Citadel governments.
- A large amount of Company0051's background is detailed in supplementary artwork, including the history and locations of the Chief's scars and the names and designs of everyone in the encampment. It's well worth checking out.
- Most of the world-building in Miracle Child takes place on the work's Tumblr rather than in the story itself. This is understandable, since bogging down the work with tidbits on how the Alternian Empire works and what the various canon characters are doing would quickly leave no room for the plot.
- Flowing Star: The final notes of each chapter has additional information about the setting, lore and the characters from the story.
- Blood and Spirit: A chapter after the main story discusses how Arisa is able to maintain her existence as a ghost and how her powers work.
- Abraxas (Hrodvitnon): The author has provided a lot of extra notes on world-building, the characters, Comic-Book Fantasy Casting and What Could Have Been, mainly on her Tumblr but also in the AO3 comments section.
- Oversaturated World: Some background details of the verse aren't covered in any of the fics proper, but on the group forum FAQ. There are even details from an otherwise unrelated series of oneshots and an old blog post by the author thrown in, the latter of which is for chromelanin.
- The author for Kitsune no Ken: Fist of the Fox has a DeviantArt account where he posts drafts of story-notes, which he had set up as a way of giving some closure in case he ever decided not to update the story further.
- Advice and Trust: In the thread in the Sufficient Velocity forums, Strypgia provides with supplementary notes and commentary to understand the story and the characters.
- A Crown of Stars: Strypgia provides commentary and insight in the story, and even clarifications about the many shout-outs in this thread.
- HERZ: The author included supplementary, world-building notes after every chapter and in an F. A. Q. in his site.
- RWBY: Destiny of Remnant: Some fellow authors who collaborated with UGX7 wrote some short stories to fill the gaps.
- Another fellow author, GojiGrimlockSaurus, wrote a World of Remnant-styled short story about the dinosaurs, as well as a "trailer" for the upcoming third story arc. The World of Remnant can be read here, while the trailer can be read here.
- Another fellow author, GojiGrimlockSaurus
- Skylanders: Return to the Ruins: Crestfeather's Toyhou.se profile reveals her birthday is January 18th, which is never mentioned in the fic itself.
- A Raven Under the Starlight: The author SyfyGuy2's take on the Far Side of the Atmos is described in even further detail beyond what this fic shows in a series of lore dumps, which can be found on his old Tumblr blog under this tag, and can also be found in a single comprehensive entry on his DeviantArt journal here.
- Courtney and the Violin of Despair: Includes a substantial Notes section. The narrative and notes also include hyperlinks to supplemental information on ancillary topics and embedded music videos for some of the compositions mentioned.
- Legacy: The story includes hyperlinks to supplemental information on ancillary topics, including the song that became the basis of Trent's tribute song.
- Total Drama Island by Gilbert and Sullivan includes an extensive glossary, as well as many hyperlink to music files and supplemental information on ancillary topics.
- Luminosity's official website has a page to keep track of the large cast, listing the characters and their status as of the end of the second book. It also has information not stated in-story, such as that David's last name is Baxter (although this information later shows up in Flashes).
- Underverse: The series has this in multiple layers.
- First of all, to know how exactly Cross and XChara ended up in an empty world and ruining other people's lives to get it back, what the X-Event is, who XGaster is and why he's so important, and what the whole number thing is, you have to watch the XTALE prequel series and read the comic.
- In addition, Underverse is Recursive Fanfiction, which means that the viewer needs to be familiar with a whole bunch of different Undertale Alternate Universes, as the series never bothers to explain what their Origin Stories and motivations are.
- There's a lot of Foreshadowing and exposition in side material that are not part of the counted episodes, such as the Xtra scenes or the Season 2 prologue. Without watching them the viewers will quickly be lost on what some characters are referring to, as there are plenty of twists.
- Finally, addition details about the lives and personalities of the XTale cast - like birthdays - are only available on the Underverse Tumblr blog.
- The Doctor Who fic Keep On Running features notes from the author, East of Akkala, on certain stylistic choices and the fate of at least one Echo!Clara.
- Arc-Ved Protagonists: Every card Kurimaster made for someone to use in a duel in this series gets posted over onto his DeviantArt (sometimes with a large gap between posts). Looking at the card's effects can reveal details that were never mentioned in the duels themselves. For example: the Fusion monster, Evil HERO Sonic Ragnarok has an effect that prevents the opponent from activating effects of monsters that have a lower attack then itself, but when it showed up, Roget wasn't in a position in which he could try to use any monster effects to gain any advantage before he lost.
- Strong and Steady: Maddie's Japanese name, Kagami, is only revealed in the tags. It is not used in the main story.
Unsorted
- Power Girl fanfic A Force of Four is set in the Pre-Crisis DC universe. In order to help readers who may not be familiarized with those versions of the characters, Dark Mark provides a glossary listing characters, first appearances... It isn't necessary to read it to understand the history, but it's helpful.
- If you want to fully understand Savior of Demons, it's necessary to read the extensive Q&A at the end of each chapter. It also helps to refer to the SoD Special Forum, where the author personally responds to queries.
- Code Geass: Colorless Memories Has a good deal of this with the following places containing much information not stated in the Main fic.
- Companion fic Code Geass Colored Memories, it's main focus is on the POV of Kaguya, Suzaku, and Kallen. It also adds background stories to many characters like Colonel Kusakabe. It fleshes out other events that happen before or during the timeline of Colorless Memories, along with worldbuilding the Code Geass universe in more detail.
- As mentioned above, the pages on Code Geass fanon wiki, there is information that is not stated in the main story that gives more information on the fic's universe, such as details to many of the Knightmare Frames, the thought elevators, full character list and information on each of the factions.
- Along with a work in progress Colorless Memories Timeline of the fic's universe.
- A number of the pages also include quotes, conversations, and teasing of possible future developments in the fic's.
- Along with a work in progress Colorless Memories Timeline
- Companion fic Code Geass Colored Memories
- In Supergirl fanfic Hellsister Trilogy, helpful character lists are provided so nobody gets confused by the Pre-Crisis characters' backstories.
- In the Mobile Suit Gundam Wing Crossover fanfic Demon of Justice a list of the Gods of Norfressa is provided. It differs from the canon version from the Oath Of Swords books. This is a plot point.
- In the Lyrical Nanoha fanfic Academy Blues (As recommended here.) If you want to fully understand how some characters' powers work, and the personality of many of the characters, you need to read the review replies the author gives, as well as read the side stories for the series. Which is ironic, given that the author has declared his dislike for this.
- Evangelion 303: Grummancat often gives extra information in his DeviantArt page about the story, characters and backstory, clarifies doubts and explains how he came up with some concepts (such like Asuka's Cool Bike).
- RWBY: Destiny of Remnant:
- RWBY: Crucible author, RelentlessCrusader, wrote a character short-styled story about the Remnant Knights, and what they have been up to in between the second and third story arcs. The story can be read here.
- Cosmic Fiction has written a prologue of sorts that references the Relics for the upcoming fourth story arc. The story can be read here.
- UGX7 himself dedicated an entire chapter giving information of every character thus far up to chapter 52, both canon and OC, as well as their current statuses at the time. Additionally, the author also listed recommended music themes for certain scenes in the story. It can be read here.''
- RWBY: Crucible author, RelentlessCrusader
- Renegade features a number of Codex entries similar to the Codex in Mass Effect that details additional notes about the setting.
- This is actually a recurring trend in Mass Effect fanfiction. Particularly with Halo crossovers.
- Many details in The Great Slave King only appear in the author's notes and responses.
- Between My Brother and Me: In-universe: May and Max learn all they need to know about dueling from a magazine called 'Duelist Monthly'...that their mom had for some reason. From it, they learned about Duelist Kingdom, Battle City and the 'who's who' in the world of dueling.
- The Legend of Total Drama Island includes an extensive Notes (aka trivia) section, which mainly explains the more obscure allusions. In the Wikia-based version, the Notes also include hyperlinks to supplemental information on ancillary topics, mostly things alluded to in the story, and the story itself includes embedded music videos for most of the compositions mentioned.note
- The tumblr on which the Ragnarok Online fanfiction Warriors of the World is posted is occasionally updated with a post tagged as "lore" giving background information regarding the many changes to the world of Midgard in order to have it work as a real world. On top of that, the author has stated that this is exactly what the tumblr is for since they got tired of having to reply to their own reviews on FanFiction.Net.
- Hivefled has a tumblr which provides additional information and worldbuilding on a lot of the characters.
- After The God Empress of Ponykind was completed, the author began a series of blog posts dedicated to expanding upon Equestria and the history of the different factions present in the universe.
- The author of Horseshoes and Hand Grenades has their fanfiction.net account that gives up a list of background info about the characters.
- The official wiki for the supercrossover military fanfiction series, The Terminators: Army of Legend, contains extra content not found in the story itself, everything from operation names to casualty lists, as well as background Intel on specific locations and battles.
- CertainDestiny, the author of Soul Eater: Troubled Souls, posts on his DeviantArt account (Grade-AMasterpiece) character profiles for the Original Characters that appear in the story. He also puts up glossaries that explain original concepts.
- ParadoxProphet, the author of Despair's Last Resort has been making posts going into further details on her Tumblr, and intends to make other posts going into aspects of the story that couldn't be explained in the story proper. She also is writing Resort Mode chapters, which go into the unused free time events of the characters and gives a better idea of what they're like.
- The KanColle fanfic Pacific: World War II U.S. Navy Shipgirls is heavily reliant on this and Word of God, to the point that two separate supplementary works, called Aeronautica and Action Report have been announced or released to accompany it.
- Similar to the Renegade example above, fully half of the Mass Effect/Sword of the Stars Fusion Fic Shepherd Of The Stars is comprised of Codex chapters that explain more about the setting and sometimes supply important plot points. Considering how lore heavy both universes are, this is probably to be expected.
- The author of Young Justice: Darkness Falls and Young Justice Titans uses this pretty heavily, though that also follows somewhat in the tradition of the show introducing characters into storylines without a "proper" origin. Probably most blatantly done at the beginning of Titans, where the author gave full drawings/bios for the titans, including giving origins proper for Arrowette and Kyle Rayner without them being seen onscreen.
- Oversaturated World: Some background details of the verse aren't covered in any of the fics proper, but on the group forum FAQ. There are even details from an otherwise unrelated series of oneshots and an old blog post by the author thrown in.
- Pokémon: Nova and Antica: The writer has a whole section in his DeviantArt gallery dedicated to the additional elements and the Original Characters introduced in the story, meant for easy access to brush up on or familiarize yourself with the content. This includes commissioned artwork of his Original Characters. To a lesser extent, Pokemon Story Chronicles also serves as one.
- Forum of Thrones has its own wiki, which is stated to include additional background information that has no room in the actual story, but can still be treated as canon to it.
- The trope page is often frequented by the author, who uses it to establish minor details that may or may not be brought up in the story proper later on, such as the names of minor lords or the exact nature of some events.
