What age group is this costume for?
Preschool and Younger
Elementary School
Middle School
High School & Beyond

Estimated time required to make this costume:
An hour or so

Difficulty level:
Quick and easy - no sewing required

Items you will need: (Hit your return key to start a new line)
cardboard
elastic or string
yellow paint
black marker
backpack
canteen
hiking boots
walking stick
hiking shorts (only if its warm where you live!)

Instructions:
Cut a large circle from the cardboard, a little larger than your face. Cut eye holes. Paint yellow and draw the smiley face on when the paint is dry. Staple elastic which is long enough to hold mask on, or staple string on each side to tie mask on. Dress in camping gear and whistle "My Knapsack On My Back" as you trick or treat.

Other information to consider:
I'd only wear the shorts if it's warm outside. You could wear thermals underneath I suppose.