The Bun-Bun Brothers

From Muppet Wiki

The Bun-Bun Brothers are a group of rabbits who sang "Zip-a-Dee-Doo-Dah" on episode 420 of The Muppet Show. They almost never got the chance however, as Kermit originally turned them away for a performance due to show business politics: if he had singing rabbits on, he'd have to cancel the dancing carrots. The Bun-Bun Brothers get their wish when they go on in place of Alan Arkin, who has become incapacitated from Dr. Bunsen Honeydew's Ultra-Powerful Jekyll-Hyde Potion. Their fifteen minutes of fame are cut short when Arkin appears on stage to mercilessly ravage the fluffy bunnies. They exact revenge by show's closing when they get a dose of the potion.