As his name indicates, Fatty Whale is a fat blue whale, nearly the size of the room that is his battle arena. In his closed mouth, it holds a wooden pipe. It also wears a white collared shirt and red neckerchief.
Upon his defeat in the remake, Fatty Whale gets a bandage on his cheek.
Fatty Whale's strategy, besides attempting to ram Kirby with his body, is using his blowhole to blow out boulders (which yield the Stone ability when inhaled and swallowed) and sometimes Blippers, which proceed to fall from the sky.