Iceberg Lettuce Bird is yet another bird based off a plant from Plants VS Zombies. Really, it's just lettuce with a beak.
Upon activation, a bubble forms around it. This bubble will then grow to a ginormous size before evaporating. However, if a pig happens to enter the bubble, then the expansion will come to a premature stop. After that point, it's basically Ice Bird, except it only works on pigs.
By the way, Iceberg Lettuce Bird does not have a brain. Yet, it can detect if you feel sorry for its lack of a brain, and it would prefer if you didn't.