My idea for this costume came when I had a beverage holder and I needed a costume. I decided to make a simple and fast costume. It took me 30 minutes to make this but that includes moving fairly slow, finding materials, and coming up with how to make it.
You put off getting a costume until now. The costume store is completely unoriginal. In retrospect, Playing video games until an hour before the time of costume need was not such a good idea. Here is an awesome project idea for those with little time or supplies. Blah blah blah... lets get started!

You need:
a beverage holder
string(or elastic)
red shirt
red fleece pajama pants(cheap at target)
construction paper(red, white, and black)

tools:
hot glue gun(turn it on before you start)
hole punch
scissors

Step 1: Cutting

First you need to cut the beverage holder to size. The exploded pictures show exactly where to cut it. The smallest pieces will be trash, medium size will be trash, and largest will be mask base. You may want to trim the mask base a little more, like I did for the next step, so that it will all fit behind the mask front.

Then, you need to cut the construction paper. you will need one large triangle with two holes(eye holes make them to your size) for mask color base, a black trapezoid, and many small white triangles for teeth. Also you will need two medium sized donuts(to go around the eye holes, size appropriately) and two horns(size is optional on the horns). The horns are irregular so check out the photo. The picture shows the relative size and setup. All sizes are relative to the size of beverage holder that you have.

Step 2: Gluing

First glue the teeth to black trapezoid, then glue the trapezoid and the donuts shapes to the triangle. After that, glue the triangle down on the beverage holder so the beverage holder is upright and the triangle is on top of it. Use the raised up points of the beverage holder to glue the triangle down. Glue the horns on as shown.

Step 3: Finishing Touches

Once you have glued on the top, you can use the hole punch to punch holes for the string(you may want to have two holes per side). The holes should be near the edge but at least half an inch away. Then run the string through the hole, put the mask on, and pull the string nice and tight. Hold the string, take off the mask, tie the string loosely, check how the mask fits, then tie it tightly. If you are using elastic, pull it tight and staple it.

You now need to wear your red shirt inside-out and your fleece pajama bottoms along with the mask. Viola! costume!