Grim challenges the kids to a game of limbo; Billy's mum is afraid of Grim; Opposite Day and everything is in reverse.

Without the R, Billy and Mandy are kidnapped by another supernatural creature. Grim must decide who he'd rather rescue.

While on a Halloween excursion, Grim finds himself mistaken for a young boy named Gregory. Now it's up to Billy and Mandy to return Gregory.

Billy develops an evil growth; Grim must evade extermination; Grim builds Billy a new Mandy out of old toys.

Billy and the Bully Billy runs afoul of Sperg, the school bully. With the help of Mandy and Grim, will Billy get Sperg to leave him alone?

In a future time, in a future place, Mandy rules the world. But not everyone is happy about it. Erin returns.