Dragon Ball Season 1 Episode 13

Goku and the others have been captured once again by Pilaf. That night, Goku looks at the full moon, and suddenly turns wild and starts transforming into an Oozaru!! He smashes the prison that they are imprisoned in, and Yamcha and the rest manage to escape, but having lost his reason, Goku continues to rampage!! Yamcha then cuts off Goku’s weakness, his tail! Goku wakes up after returning to normal. The party promises to reunite, and the Dragon Team splits up.