What age group is this costume for?
Preschool and Younger

Estimated time required to make this costume:
10 minutes

Difficulty level:
Quick and easy - no sewing required

Items you will need: (Hit your return key to start a new line)
An old white pillowcase (one you won't use anymore)
Black eye liner or black/white makeup
Scissors

Instructions:
Put the pillow case over just the top of the head and pinch the material where the top of the forehead starts. Then, still pinching the pillow case, remove pillowcase from the head and get the scissors and cut a circle out from the pinched area in the direction of the bottom of the pillowcase. This is for the face, so you might be able to guess the size to cut.
Then, put the case back over the head and pull the case down over their arms. Pinch one side, where the top of the shoulder is. Then, take the case off, still pinching the area. Lay it flat and cut a half moon shape out, guessing the size. Then fold the case over and cut out the arm hole for the other side.
When you are done all of that, put some black or white makeup or eye liner around their eyes, or put the white all over the face.
Put the pillowcase back on, but with their arms up in the air, and pull down all the way. Away you go! All done!

Other information to consider:
You could even try it with a white crib sheet that you won't use anymore. But you can use this costume over and over again. I did!