S06E24 Lemon of Troy
Shelbyville kids hijack Springfield's sacred lemon tree after being pelted with lemons, and Bart leads a guerrilla war against them (I say a war, but it's nowhere near violent.) They find out that the tree is in "the impenetrable fortress of suburbia"- a car impound lot, owned by the leader's (Shelby's) dad. Homer and the parents of the kids find them and team up with them to get the tree back. But how are they gonna get it from a car impound lot?