The Ice Cream Costume is a costume that was a part of an Account Upgrade with the Nightmare Costume in Feb 2013 and is now retired. If you put this on your pet, they will be covered in ice cream and have some waffle 

Rarity 29

19 icecream

The Easter egg

cones to replace some features of their body (like feet). Althoush the costume is pink and brown, Ice Cream pets vary in color.