http://www.ecocitycraft.com/forum/threads/pet-bug-no-face-sheep.108059/

Brief Description: sheep are left with no face or nametag

Instructions: do /v while your pet sheep is showing

How many times did you recreate this bug?: three times/two different users

Result: The sheeps nametag and face vanish

Expected Result:The entire sheep is supposed to vanish

Evidence: none

This isn't something I can control - it's rendered by the client. Throw an invisibility potion on a sheep in vanilla and you'll get the same result :).