The Pixar universe
The Pixar universe is a theoretical "shared universe" in which every character that is created by Pixar exists, sharing characteristics and an internal logic. Media discussion AbOUT a "Pixar Universe" has existed since at least 2003, and has been referred to in disparate sources such as Slash Film, Washington Times, Reno Gazette-Journal, and MTV News
Pixar employee Jay Ward denied that the films take place in the same universe, saying: "It's almost like the 9/11 conspiracy theories... it's like, really? No, the movies were sort of made in a different order by different directors in different times, in different places. It's cool that it all worked out that way, but it probably was not intentional."
In To Infinity and Beyond!: The Story of Pixar Animation Studios, Karen Paik states that there are many internal references between various films in The Pixar Universe. In 2009, CityNews Toronto made comparisons between nine "Pixar Universe" films.
In his 2013 thesis entitled "The Pixar Theory", Jon Negroni wrote that every character created by Pixar lives within a single fictional universe. He acknowledges that the concepts behind his thesis were derived from an episode of the Cracked.com video series After Hours, written by Daniel O'Brien. In his post, Negroni discusses various films and how they relate in a timeline of events. Films he examines include A Bug's Life, Toy Story 2, Monsters, Inc., Finding Nemo, The Incredibles, Cars, Ratatouille, WALL-E, Up, Toy Story 3, Cars 2, Brave, and Monsters University. After his thesis was posted on the internet on July 11, 2013, it became a viral hit. IO9 wrote Negroni's work is "a crazy read, one that Negroni has been annotating as readers point to corrections or flaws in his theory. But even as a tinfoil hat theory, it makes some clever connections—and, of course, contains plenty of Pizza Planet trucks."