The Headless Costume is a costume that can make your pet headless. To get a chance to make your pet
Costume headless
3 headless

The Easter egg (notice the yolk and egg whites that somehow turned red)

headless, you can go to the Guillotine which is right here. This costume is Rarity 33. You can also view the Headless Costume here. Headless pets are blood red, have blood spewing from their necks, and Headless Xoi (below) proves to us that its body is just a head.