3. Boo from Monsters, Inc. grew up to be the witch from Brave.
She grew up missing "Kitty" so much that she devoted the rest of her life to finding him, and she did so, using the doors in Monsters, Inc. A carving of Sulley also appears in the background of Brave, fueling the idea that the witch knows who he is.
4. In Toy Story, Andy's parents are going through a divorce.
This theory's been around for awhile, but makes sense: We never see his dad, he's not in any family photos around the house, and his mom never wears a wedding ring.
5. ... or his dad is dead.
Andy's very attached to his two toys — both strong males — which seem to represent the missing father figure in his life.