From the Super Mario Wiki
Mummy Guys are undead Shy Guys appearing in Mario vs. Donkey Kong 2: March of the Minis. They are just like Mini Shy Guys, however when stepped on they will break apart like Dry Bones and grow back after some seconds. Mummy Guys appear in the Spooky Attic. It appears, like many other enemies, that these toys also have a life of their own. Even if they are toys, they do not have "mini" in front of their name.