Saddle Rash (2002)

S3E20 Our Vines Have Tender Apes

A loincloth-wearing ape-man named Tongo arrives on the island and steals the Castaways' food and supplies. However, he’s actually an unemployed actor preparing for a role, attempting to convince everyone that he’s a genuine savage. When he encounters a real gorilla and panics, his façade crumbles. Ultimately, Tongo decides to leave the island and the Castaways behind, revealing the truth of his charade.