"A foolish consistency is the hobgoblin of small minds."
-- Ralph Waldo Emerson.
In a large franchise with many works and contributors, how do you determine what is canon?
Usually, fans rely on the creator or publisher of the work to directly state what is part of the official continuity. Often there becomes a defined hierarchy of canonicity designed to resolve contradictions between works - i.e. one work is "more official" than another and will always supersede another.
But what happens when the owner of the work embraces the contradictions? What if the line between canon and Apocrypha is deliberately blurred in order to make a statement about relativism?
Some universes eschew the concept of a "definitive" continuity. After all, the real world is full of vagueness, bias, and conflicting accounts. It can be a real puzzle for fans to try to piece together a picture of "true events," and of course no one’s guess is actually wrong.
In short, Unreliable Canon is when the creators of a franchise encourage their audience to call the truthfulness or authority of so-called official canon into question, while allowing less official parts of the verse to enjoy equal or near-equal status.
This type of franchise usually combines some of the following situations to create deliberate vagueness:
The work contains a Featureless Protagonist who remains genderless/raceless/nameless even when referenced by subsequent titles. Especially in a roleplaying game, where the actions/decisions of this character will be left vague in sequels, and any hints about what happened will be presented as wild rumors.
Major elements of the story only make sense in the context of unpublished or unofficial material, or even well-known fan-works. This creates conflict among fans as to whether said work is now "official".
Compare with Broad Strokes, where chunks of a previous work are ignored in the sequel, Armed with Canon, when multiple authors try to undo one another's work, and Shrug of God, where an author gives up trying to explain how things work.
Often done by Teasing Creators. In Death Note the finale ends with Matsuda stating a bunch of theories that may or not be true. It doesn't help that in The How To Read 13 Obha simply says: "Death Note is about the reader's interpretations".
The Star Wars Expanded Universe is official canon (conflicts are decided case by case, but generally novels are ranked highest, comics next, then video games, then RPG sourcebooks). But yeah, Lucas doesn't care about it, causing no end of problems in retconning the EU to match up with G-canon (the movies and any materials directly connected, such as the novelizations, Visual Dictionaries, and Incredible Cross-Sections). The continuity problems are one reason Karen Traviss quit.
The Muppets could very well fall into this trope, whatever "canon" there might be for the characters has always been rather vague and up for discussion for fans, for a variety of different reasons, including the fact that sometimes different shows and movies aren't necessarily within the same continuity. It also doesn't help that Jim Henson himself never considered the Muppet characters actual characters, but rather, a troupe of actors that just happen to be puppets (hence such movies as The Muppet Christmas Carol and Muppet Treasure Island).
Early Discworld novels often contained contradictory elements, because Pratchett was more concerned with the quality of the story than with consistency, citing the famous Emerson quote. Later, he adopted a more consistent canon, but those early stories have still have a hard time fitting with it.
The novels in John Varley's Eight Worlds series frequently contradict each other when it comes to matters that could be called canon. Varley has admitted that he doesn't like going back to re-read his old works, and doesn't really care about the overall canon.
Doctor Who, especially before the New Series, can be best summarized as existing in a state of constant flux. Not only did you have the TV show introduce a new concept that gets changed to outright retcon after a few years, convoluted timelines for UNIT and the Daleks, but you also had several lines of novels that came during the show's hiatus. This isn't helped by the fact that the New Series sometimes makes references to the books and that the New Series itself doesn't follow certain things from the Classic Who (the aforementioned Daleks' timeline for example). This is not even counting the comics, the novels and the audio stories for the New Series. And let's not even get into Big Finish...
This is often done deliberately in Tabletop Games, both as bait to get people to buy supplemental rulebooks, and to offer individual GMs maximum freedom in constructing their own campaign storylines.
In Nomine went so far as to document areas of "Canon Doubt and Uncertainty" which would never be resolved by supplements.
Both In-Universe and out in Warhammer40K, where misinformation and plain lack of information is visible at all levels of classification. For example, in order to avoid lowering morale anymore than it already is, the Imperial Guardsman's Uplifting Primer states that orks are cowards who will flee at the first opportunity and whose teeth can be yanked out (orks are eight-foot-tall killing machines who embody Attack! Attack! Attack!) or that the Tau (the army dedicated to ranged firepower) have bad eyesight and can't see things that don't move. And as most of the information on other races comes from a xenophobic human point of view, what information is canon may not necessarily be true. Out of universe, you can create your own highly specific army with its own backstory and design (most popularly, Space Marines) precisely because of this loose canon.
Shadowrun. Most early edition supplements had a statement like this in their introduction. Like previous Shadowrun sourcebooks, this supplement is formatted as an electronic document from that fictional world. Scattered throughout the document are comments and additions from readers who seek to correct, expand, corroborate or contradict the information it presents. Because this "black" information comes from characters within the game universe, players or characters cannot safely assume that these comments are truthful, accurate, considered or clearly thought out (though they may be all those things). The material in this supplement comes from a variety of sources, most unofficial and all with their own biases built in. These different points of view give gamemasters greater scope to decide how much of the information presented is accurate, misleading or false in their own games.
In The Elder Scrolls universe, canon is an almost meaningless concept. Bethesda refuses to invalidate your choices about who your character is and what he/she does. Therefore, there is no definitive version of the Nerevarine/Champion/Dragonborn, etc. and very few canonized events (the main quest line usually being an exception.) Additionally, all in-game information, books, and historical records are biased or otherwise unreliable or contradictory, with the implication that All Myths Are True and everyone is right in spite of the contradictions. From a meta-perspective, canon is complicated by the fact that the majority of the lore that elucidates the nature of the world of Tamriel comes from the work of an ex-dev and were written in an unofficial capacity after he left the studio. Many lore-scholars within the fandom actually consider his work ‘more’ canon than the published games themselves, and the fact that the games reference and quote these works adds to the confusion. Rather than become frustrated, fans tend to embrace this ambiguity as one of the more fascinating elements of the series.
The background lore of World of Warcraft has grown quite complicated. Different races tend to tell conflicting stories about such details as their races origins or past history and Word of God says that they are suppose to be conflicting; every race has a biased/distorted view and so none one race's myths are completely accurate. Then there is the ambiguity of major plot events, such as rather a certain Naaru may have intentionally let itself be captured as a ploy to help blood elves find redemption. And all of this is before you count the numerous actual retcons.
The various games in The Legend of Zelda franchise have many characters and sometimes place names in common, but they don't fit together neatly into a single continuity.
In the early days of Sonic the Hedgehog, the in-game stories are simple Excuse Plots about Dr. Eggman trying to rule the world through robots, with Sonic stopping him. SEGA encouraged production of alternate storytelling media, resulting in atleastsixgroupsofpeople working independently on their own interpretation of the franchise, each with their own continuity totally separated from the video games. With the exception of Sonic X, which came later, most kids in the 90s accepted at least one of these adaptations as canon with the video games, a precursor of the franchise's infamous Broken Base today.
The Touhou series is as much a product of its fans as it is its creator, who works mostly by himself. Anything made by the fans that achieves Memetic Mutation becomes part of canon, including character artwork, behavioral traits, backstories, even including fan-made games. Anything that achieves Memetic Mutation that contradicts something else that previously did the same receives a justification.
Valve Software once stated that 'canon is uncanonical' to reserve creative freedom for the Half-Life series of video games.
Homestuck, specifically the Word of God coming from its Trolling Creator. Andrew Hussie frequently answers fan questions with blatant nonsense and a sarcastic tone--but sometimes that "nonsense" actually turns out to be true. For example, after Tavros and Vriska died, Hussie jokingly confessed that he was planning to bring both of them back to life--then, months later, they actually did come back (albeit in the form of Tavrisprite, who only lasted a few panels before exploding). Which leaves the fandom unsure of how to take his other claims, like "Sollux's full name is Solluxander" or "All fantrolls are canon"...
This is the general idea behind The Fear Mythos and the only way to be a fan of every version of every Slendermanwebisode series without Dis Continuity derailing your enjoyment of each. It helps that each monster is an Eldritch Abomination and the bending of reality isn't hard to believe, but when everyone is going a different way with the interpretations, you just have to let some things slide.
Done deliberately in the SCP Foundation, since it's built on a crowdsourcing model, and allowing for multiple interpretations (i.e. Dr. Clef as an abrasive researcher / a Reality Warper / Satan himself or the Foundation as a Men In Black organization trying to save the world or control it).
Five hats means that five tropers think it is ready to publish.
You are saying that you think this draft is ready to be published. That means the description is not ambiguous,
it doesn't duplicate an existing trope, there are at least three examples, and the title makes sense.
Is that what you meant to do?
You are saying this draft has a ready-to-publish hat it does not deserve and you are taking it back.