Bully Boogie (S03E14)

Feeling defeated after failing to frighten a fifteen-year-old, the Boogeyman seeks out his former middle-school target, Grim. Grim recalls Boogie’s past as a bully and insists on receiving an apology. In response, Boogie vanishes into the Underworld, taking Billy along. Determined to confront him, Mandy and Grim pursue. To resolve their issues, Mandy proposes a scaring contest, where the one who terrifies a child the most will emerge victorious. Although Boogie's werewolf form falls flat, Grim's transformation into an enormous, terrifying rubber duck proves to be far more effective.