The Simpsons II:Journey to the 5th Dimension

Characters
Lord Darkness(Herb)-Homer's long-lost half-brother.

Plot
They set course to Earth, but after a call from Abe, the family plans to go anywhere else but home. Bart and Lisa tries to escape in Lou's police car, but Lou gets transformed into a plant and surely after, Bart and Lisa are infested. Then, the credits happen while a fan cover of the main theme from Blackadder plays over a flying shot of a post-apocalyptic Springfield