Alright so I'm pretty sure this is a very common, extremely talked about topic, but i thought i would share anyway.
Pixar Theory:
The Pixar Theory, put simply, is that all Pixar movies take place in the same universe. It is believed that it all started with Brave. All animals and other creatures gained the ability to talk with the witch in Brave’s magic. And it is believed that that is why, later on down the timeline, animals can talk, like in Up and Ratatouille.
In the movie Up it is believed that some kind of industrial revolution is happening because of B&L and that B&L is the reason why the humans in the movie Wall-E escaped to space.
This theory is super long and confusing and quite simply a pain in the ass. I recommend googling it because like its too long for me to ramble on.
Tarzan Theory:
This theory suggests that Jane from Tarzan is the granddaughter of Belle and the Beast. People believe these because of how similar the two women look, they both seem to be attracted to beast like men, they both have weird fathers, blah blah blah.
The Emily Theory:
This theory is definitely one of my favorite movie theories to-date. Supposedly, Emily, Jessie’s previous owner, is Andy’s mom. After three movies, we never actually learn Andy’s mom’s name. Andy is seen wearing an almost identical hat to the one Emily wears in Jessie’s flashback. Also when Emily is dropping off all of the items including Jessie, the hat is not there. Plus, Emily’s room is decorated in a retro way that would’ve been common for the time Andy’s mom was growing up. In every Toy Story movie, it’s often brought up how rare and valuable Woody is. Wouldn’t it make sense if Andy’s mom had found the boy version of the toy she loved so much growing up?
The Trio Theory:
By now, you’ve probably seen the picture floating around the Internet of Rapunzel and Eugene at Princess Elsa’s coronation. There’s a very possible theory out there that Elsa and Anna are cousins of Rapunzel. Because some people think that Elsa and Anna are Rapunzel’s cousins, it’s entirely possible that their parents were on their way to Corona for Rapunzel’s wedding when their ship wreaked. Going even further, some people have questioned whether or not the shipwreck Ariel discovers in The Little Mermaid is actually the King and Queen of Arrendelle’s ship.
I also just recently read that some people also believe that Anna and Elsa's mother was pregnant at the time they set sail, and that Tarzan is actually Anna and Elsa's brother as well. Some people believe that when the ship wreaked they ended up washing up on sore and giving birth to Tarzan.
Up Theory: