This theory is fun but super complicated. It involves time travel and a whole bunch of magic but basically, Boo learned how to travel through doors from Sully and Mike in Monsters, Inc., right? So when she grows up, she wants to find Sully again so she time travels through doors to the time period of Brave. Why? Because she wants to understand the magical whisps, thinking they'll bring her back to Sully. While she's there, she takes up wood carving, which explains why she has a carving of Sully. It also explains why every time the door closes, the witch (AKA Boo) disappears.Believe it at your own risk or choose to decide agaisnt it.
