Boo’s real name is Mary Gibbs, but she was named Boo by Sully in Disney Pixar’s Monsters, Inc because she frequently exclaimed “Boo!” for fun. She’s a human toddler who is curious and not at all afraid of monsters, except for Randall, the monster that was assigned to her. Boo ventured through her closet into the Monster world and became attached to both Sulley and Mike Wazowski. She can only say a few words and calls Sulley “Kitty!”. In Monstropolis, Boo was perceived as a threat to public health. Although Mike was at first reluctant about contact with Boo, the three developed a friendly bond. After finding out that children who laugh bring positive energy to their world, Boo was returned home safely where Mike and Sulley often visit her. Together, they also like to visit Disney parks.