Simply put, this is when things happen in a work because out of universe reasons, with none in-universe reasons behind it.
Characters will dissapear or be abruptly killed off because the actor commited a Role Ending Misdemeanor, characters fail to show up in a work because of copyright disputes, something is vilified or deified because of Author Appeal, and so forth.
Fans will usually come up with several Watsonian explanations of their own, but the fact remains that the reasons for what just transpired are purely Doylist.
Not to be confused with Real Life Writes the Plot, in which real life events affect the plot, but there IS a legitimate in-universe reason for the events.
- Despite the new Terminator movie not considering Genysis canon, the T-800 still has the "aged skin" from that movie because Arnold Schwarzenegger is reprising the role.
- The characters from the MCU TV shows never appear in the MCU movies because of bad blood between the TV and movie division. Same reason why Phil Coulson is considered to have been Killed Off for Real as far as the movies are concerned.
- The invasion in the Red Dawn remake comes from North Korea, despite North Korea not having the resources for a full-scale invasion of the U.S.A. This is because the invaders were originally meant to be Chinese, but China is a lucrative film market that the studios can't afford to offend, which is why they were changed to North Koreans in post-production.
- The bad blood between the TV and movie divisions mentioned above is also the reason why none of the MCU movie characters show up in the MCU TV shows (and when they do, it's always secondary characters, never the actual protagonists of the movies).
- In the Wild Force episode "Forever Red", Leo Corbett appears morphed and then unmorphs to morph again along with all the other Red Rangers due to Danny Slavin being a late addition to the episode.
- The A-Team never hits anything with their guns due to the show being family-friendly.
- The main character of Manimal only transforms into a panther and a hawk despite being able to transform into ANY animal because the people in charge of the show only filmed Transformation Sequences for a panther and a hawk.
- Several contributors no longer show up in the Nostalgia Critic show due to the Change the Channel Controversy. It's the same reason Nostalgia Critic himself and Cinema Snob are unlikely to appear in Atop the Fourth Wall.
- Pre-To Boldly Flee, Nostalgia Critic's parents were depicted (or at least, remembered by Critic) as being cartoonishly abusive. When they do show up in the Post-To Boldly Flee episodes, however, they are depicted as kind, caring, gentle and friendly. And Critic's mother dying is played as a Tear Jerker, with Critic being in sincere mourning. There's no Watsonian explanation for the discrepancy, but the Doylist one is that these are Doug's real life parents, and he isn't willing to have them act as worse than how they actually are, and Doug is obviously legitimately hurt by his mother's passing.
- The original version of How Frozen Should Have Ended was flagged for content, which is why in the current version the X-Men don't sing "Let It Go" despite that clearly being the appropiate song for the occasion.
- Wolverine and Deadpool stopped showing up in Ultimate Spider-Man due to Fox owning the TV rights to those characters at the time.
- Bluestreak and Cliffjumper disappeared from The Transformers due to Casey Kasem (who is Lebanese) being deeply offended by the Middle Eastern stereotypes in the episode "Thief in the Night".
- Derpy in My Little Pony: Friendship Is Magic is never referred by name and hardly speaks due to the controversy surrounding her intial appearance in "The Last Roundup".
- King Louie never shows up in House of Mouse due to a conflict with the family of Louie Prima
- The Jonny Quest characters in The Venture Bros got renamed and then stopped appearing altogether due to Warner Bros not liking what the show was doing to those characters.