Billy wants to join Sperg's garage band, "Purple Filth", and take part in the upcoming battle of the bands. However, after witnessing Grim's prowess with the electric guitar, Sperg invites Grim instead. Then, Billy's dad, adopting the rock and roll persona of "Mogar", decides he and Billy should go to the contest to make a surprise appearance. In the end, Billy impresses the audience with his armpit sounds.