Geese

The Geese were the main antagonists of "A Bunch of Full Grown Geese". They were a foursome of Canadian Geese who sought nothing more than to claim the Park as their own personal territory, and attempting to do so by violently attacking anyone who intervened. In battle mode, they become a giant robotic-bodied entity with four goose heads, similarly to their young counterparts. They were the arch enemies of the Baby Ducks. The Geese were eventually killed by a giant fist from the Duck Man.

Goose Monster
The Goose Monster was the Geese's transformation. The Goose Monster had the ability to fire energy beams and missiles dubbed "Scrabble Missles". The Goose Monster nearly defeated the Duck Man, which is the Baby Duck's transformation, until Mordecai and Rigby powered up the Duck Man and eventually the Goose Monster was defeated.