The Grim Adventures of Billy and Mandy (2001)

Season 3: Episode 20

When Billy sees his father shaving, he decides having a beard is cool and buys "Hair Raiser Tonique", a hair-growing formula. Grim casts a spell on the tonic to make its effects appear faster, but Billy exaggerates the quantity and grows hair in all his body. Billy is mistaken for the Sasquatch, and a reward is offered for his capture. Hoss Delgado also receives the tonic and is captured and exhibited as the Sasquatch, while Mandy collects the reward.