Simpsons:Hit and Run, The Easter Egg - Treehouse of Horror Car

First, you have to get to Homer's last level. Next, you go to the Springfield Cemetery, and the gates are open. While driving inside, you will see a zombie in the graveyard. Walk up to him, and he will let you buy a Purple Zombie Car. It is the zombie car the mutants used to chase homer in the Treehouse of Horror episode, "The Homega Man".