It is a brown gorilla suit with a pink chest and mouth. The costume's hands and feet are purple. The wearer's eyes can see out of the costume.
Role in episode
Patrick wears the suit in hopes that SpongeBob will come outside to save Sandy. However, a real gorilla had disguised himself as Patrick, and when he reveals himself, he winds up seriously hurting Sandy and Patrick.
Patrick wore this suit as a Halloween costume once.