This is a really cool and simple project. You could do it in an afternoon.
Step 1: Supplies
1 foam pumpkin that will fit over your head
1 2AA battery pack
4 56 Ohm resistors
Red see-through fabric
Step 2: Carve your pumpkin
Step 3: Harass your coworkers
Also if you have time look at a chart about the internet.
Step 4: Make it comfy
Step 5: Make It Light Up
I added extra hot glue around the mouth to simulate saliva.