The Muppet Show 4x20

Alan accidentally drinks Bunsen Honeydew's Jekyll-and-Hyde potion, and turns into a rampaging monster. He runs amuck, as the ultra-cute Bun-Bun Brothers sing "Zip-A-Dee-Doo-Dah." When Kermit catches Alan in a net, he turns back into himself. Soon, Kermit takes a sip of the potion himself.