Wikisimpsons:Canon
Canon is the official story of The Simpsons universe. Due to the episodic nature of The Simpsons and a floating timeline, some episodes are considered non-canon because they do not match up with the existing and future story and lore.
Floating timeline
A floating timeline is often used in media where the characters do not age. The floating timeline is used to keep stories relevant for modern times without having the characters age up. Since The Simpsons has been airing since 1989 without the characters aging, the timeline adjusts to keep up with the current year. As such, characters have been different ages in different time periods. For example, Homer has been a young adult in the 1990s, as seen in the season 19 episode "That '90s Show" and a teenager in the 1990s, as seen in the season 32 episode "Do PizzaBots Dream of Electric Guitars?". These episodes are considered canon, just canon at different time periods.
Separate canons
The Simpsons executive producer Matt Selman has said that he considers episodes to take place in "its own little universe". This allows them to write about an "aspect of Springfield that hasn’t been examined before."[1] This means that there's no official canon within the show.
However, some events from episodes do carry forward to other episodes. Major changes happen in the show that continue to other episodes. Big examples include Maude Flanders' death in the season 11 episode "Alone Again, Natura-Diddily", the Ned Flanders and Edna Krabappel relationship in the season 22 episode "The Ned-liest Catch", and Comic Book Guy's marriage to Kumiko Albertson in the season 25 episode "Married to the Blob". These permanent changes imply that there is a canon to The Simpsons.
