Bun-Bun is Underfist's enemy. He is considered a threat to Halloweenland in the House of Animals franchise. He is a marshmallow bunny rabbit brought to life by Megatron's pollution. He is second-in-command of the V.H.O.T.S.B.T.E. Army in the Second World. He sometimes takes over Megatron's position as leader when Megatron is either injured or absent from certain episodes.