For Halloween, you could be a trash bag. What you do is cut a hole in a trash bag and wear it.
You stuff it with all kinds of empty boxes. Some Examples: Kleenex, cracker box, bottles, etc. Now you are a trash bag.
Thanks to Amy Beth for this fun idea.
Wear a garbage bag with holes for the neck and arms and stuff, and glue bits of garbage, like candy wrappers, orange peals, and olds sock, etc. to it.
Thanks to Shar for this additional idea.