Trumpeting Gnarr (Showcase) (307) [Ikoria: Lair of Behemoths] [Showcase]

Mutate {3}{G/U}{G/U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Whenever this creature mutates, create a 3/3 green Beast creature token.