Onions have two green leaves with a orange part in the center, and four blue leaves on each corner. They also have two small black eyes located near the bottom of their sprite.
Onions move around on platforms, sometimes even moving off them. They have plant creatures living inside of them, the way to kill them is first shoot the Onion, and then shoot the plant creatures when it pops out. When the plant creature comes out of the onion, neither can harm the player. If the plant creatures is not shot once out, it will go back into the onion, the player having to repeat the process over again. If the plant creature is shot, the onion and plant creature will both die.