For instance, the theory about the witch from Brave being Boo from Monsters, Inc. is only part of one major theory. The fact that Boo the witch is leaving Easter eggs behind in all of the Pixar movies as she searches for Mike is pretty mind blowing. This all ties into Jon Negroni’s super Pixar fan theory that every Pixar movie since Toy Story takes place in the same universe. He even wrote a book about it.
After you discover all of these prominent Pixar movie theories you’ll be connecting all he dots yourself. And looking for Boo, looking for Sully.