In the episode where Bart takes a concentration drug, Focusyn, Bart goes crazy when he is staying home with Lisa and Maggie while Homer and Marge are seeing a movie. When they come back, Lisa says Bart is acting funny. They go upstairs to find Bart in his room covering himself in tin foil. He yells at the family to close the door when they come in. You hear the door close, yet when the camera shows the door, it is open!