MC Costumes:

a simple datapack, that adds... well costumes! you can disguise as a mob, by having it's spawn egg in your first inventory slot. it achieves this by spawning a dummy mob that moves wherever the player goes, but it dosen't interfere with other mobs due to special tags

Great for Minigames and stealing Diamonds! (currently supporting only: pig,sheep,cow as of v0.8)