First of all, full credit for this goes to electric_piano_5k for the original idea. This is simply a derivation of his work that is meant to be cheaper and quicker to build, although not as impressive. The link to his instructable is below:
My instructable uses the same idea, but I scale it down to paper plate size. The net cost of each decoration is under 50 cents, but really you can do it for under 25 cents if you have time to order parts from China instead of other sellers on eBay.
What you'll need:
1 CR2032 or similar 3 volt button cell battery
A black marker
2 paper plates
An Exacto or similar knife
A cutting board
Step 1: Draw and Cut the Eyes
First you need to draw the shape of the eyes using the marker or any writing utensil. This is done on the part of the plate food would go on so that it will be easy to cut as shown in the photos.
Step 2: Flip the Plate Over
Once you have the eyes cut out flip the plate over. Highlight around the eye holes with the black marker, this will make them stand out. Then draw a scary looking mouth. Next grab the second plate and tape both together as shown in the photo. You really only need a piece of tape at the bottom and at the top of the plates, going all the way around isn't necessary. Finally use the marker to draw the pupils through the top plate onto the bottom plate.
Step 3: LED
All you need to do for the LED is tape it to the CR2032 battery. If the LED doesn't come on, just flip the battery around as the LED only works with voltage going in one direction. The button cell batteries don't put out enough amps to damage the LED, so a resistor isn't needed either. If you use a different type of button cell battery, make sure you have at least 3 volts or the LED won't come on or may be very weak. With the LED on, just drop in i the eye of the plates.
Step 4: All Done
That's it! Turn out the lights and the plates should diffuse the LED light pretty well.