Bart, Lisa and Maggie play a game of "Space Patrol" while Homer and Marge are out.
Lisa plays a superhero with Maggie as her sidekick, while Bart puts a jug on his head with the pretense of it being the helmet of an alien warlord.
However, his head accidentally plops into it and the jug is left stuck on his head. Lisa "frees" Bart from the jug using a croquet mallet. Lisa and Maggie then hide, allowing Bart, stumbling in a daze amongst pieces of the precious broken jug lying on the floor, to take the blame.