Billy and Mandy are a mismatched pair of youngsters who befriend the Grim Reaper after winning a limbo contest against him. Since the Grim Reaper lost, he has to be their friend, and the three go ...

At the same time, two robotic replicas of Billy and Mandy are sent into the past ... he receives a message saying that Velma, the Spider Queen, an old good friend from high school, is responsible ...