I recently read an article on the Entertainment Weekly site about X-Men: Days of Future Past. Most of the article was spent trying to sift out which bits of the X-Men movies had still happened after Days of Future Past was done with its time travel shenanigans. I don’t know X-Men well enough to weigh in on that, but it did get me thinking about the nature of canon in fictional universes.
Usually, a movie set in a fictional universe that’s had movies set in it before falls into one of two categories: sequel or reboot. Without having seen Days of Future Past, it sounds like X-Men has followed a middle path similar to that of the recent Star Trek movies. Star Trek (the 2009 movie) explicitly takes place in a timeline split off from that of Star Trek: TOS by Nero’s time travel, allowing the franchise to have its continuity cake and eat it too: the TV series still “happened”, as evidenced by the presence of Nimoy!Spock, but the movies aren’t constrained by TOS continuity. (Whether the movies have used this freedom to best advantage is open to debate; Star Trek Into Darkness does itself no favors by half-remaking Wrath of Khan.) But most franchises don’t bother trying to walk this line; they either keep previously established continuity or start afresh.
Broadening the scope from movies, this is true of any adaptation, including across media. When you base a work on an existing story, you have to choose to either accept the events of the original as established, or start over from the beginning, making changes large or small. In this way, even a relatively faithful adaptation to a new medium is necessarily a sort of reboot (see: Game of Thrones). This creates a set of sub-canons: continuities in the same fictional universe that are not necessarily consistent with each other. On the other hand, if your new work is a prequel, sequel, spinoff, or tie-in that adds to the story while remaining consistent with the original, the two works can be said to be co-canonical: both can take place in the same continuity without contradiction.
As a rule of thumb, works in the same fictional universe are most likely to be co-canonical if they are in the same medium, but there are many exceptions in both directions. The Amazing Spider-Man movies are in a different sub-canon of the Spider-Man universe (and the larger Marvel Universe) than the Sam Raimi Spider-Man trilogy, just as Tim Burton’s Batman movies are not co-canonical with Christopher Nolan’s. Conversely, works across media can be co-canonical. The Avatar: The Last Airbender graphic novels are co-canonical with both the animated series and its sequel, The Legend of Korra. The Avengers and the associated Iron Man, Thor, and Captain America movies are all co-canonical with Agents of SHIELD, and probably will be with Agent Carter as well. In general, though, splitting into new continuities is easier than maintaining consistency with old ones; this is why there are so many continuity reboots in comics. Therefore, works that have been adapted more often or into more media will generally have a greater number of distinct sub-canons. In addition to the two movie franchises and his long history in comic books, Spider-Man has been featured in a daily comic strip, multiple animated series, and an infamous Broadway musical, and no two of these works are co-canonical with each other. There are a dozen different “canonical” Spider-Men, bearing greater or lesser degrees of resemblance to one another. The differences are even sharper when a public domain character gets adapted; the incarnations of Sherlock Holmes played by Robert Downey Jr., Benedict Cumberbatch, and Jonny Lee Miller are arguably not even the same character anymore, and the BBC’s version of Merlin would have Thomas Malory rolling over in his grave. (Speaking of much-adapted fictional universes… King Arthur must have racked up hundreds of sub-canons by now, from The Mists of Avalon to Prince Valiant to Monty Python. He’s even popped up in webcomics.)
An interesting wrinkle is that co-canonicity is not always strictly transitive. The Star Wars Expanded Universe novels are co-canonical with the existing movies, but now word is out that Episode VII (which will certainly be co-canonical with the preceding movies) won’t be conforming to Expanded Universe canon. The original Star Wars movies are left in the odd position of being co-canonical with two incompatible continuities, splitting off into one of two possible futures depending on which branch 0f canon you follow. Co-canonicity can also change over time, splitting two works into different sub-canons when one introduces a contradiction or melding them together when a contradiction is retconned away or a crossover brings two previously unconnected works into the same continuity. The Doctor Who New Adventures novel Human Nature, featuring the Seventh Doctor, was consistent with the then-defunct TV series at the time of its publication in 1995. In 2007, Human Nature was adapted into an episode of the revived Doctor Who. Ironically, adapting the novel into a TV episode actually removed it from co-canonicity with New Who, because the TV series now takes place in a continuity where those events happened to the Tenth Doctor, not the Seventh.
Where am I going with all this? I don’t really know. Certainly fans get into plenty of arguments over which works are “canon” in certain fandoms, and I came up with a list of metrics that one might use–whether a work was made or sanctioned by the original creator(s), whether it’s in the same medium the fictional universe started in, etc. But really what I think is that expanded universe tie-in novels and adaptations into different media are canon; it’s just that sometimes they’re part of a different canon than other works about the same characters. Robb Stark’s canonical wife can be Jeyne Westerling or Talisa Maegyr, depending on whether you’re referring to A Song of Ice and Fire canon or Game of Thrones canon. (Which does lead to some odd Scroedinger’s-canon situations. Are Clark Kent and Lois Lane married? Yes and no, depending on which sub-canon of the DCU you’re in.) Nothing that happens on the TV series Gotham invalidates anything that happened in the Dark Knight trilogy, or vice versa. Sherlock and Elementary may not be canon with regards to the original stories by Doyle, but each of those series creates a new pocket of canon about a different Sherlock Holmes. Hence all this talk of sub-canons and co-canonicity, as a means of expressing the relationships between related works of fiction that may not take place in the same continuity.
Or this is my very long-winded way of explaining what I mean when I wonder if the Netflix Marvel series will be co-canonical with Agents of SHIELD and the rest of the MCU. Take your pick.
[Edit: And just in case this post wasn’t linky enough, here’s Kate Griffin’s post on public domain adaptations, which unlike mine actually has a point to it.]