To make monstrous mugs, your little goblins can get creative with -- what else? -- candy! Chewy treats are easy to bend and snip, and they stay in place with ball-head straight pins (choose ones that match the color of the treats so they aren't too noticeable). For hard candy, attach pieces with hot glue.
Hollowed-out pumpkins can function as candy jars when you put a bowl inside ("mummies" -- or daddies -- should saw open tops and thin out rims with a serrated knife before kids start decorating). Or pumpkin heads can lurk intact as lids atop clear candy-filled containers. Whether these creatures hover at a party or simply haunt your house, they'll be spook-tacular.
The pumpkin here is rated PG (Pretty Gross), but kids love a good gag. Put your hand under its mouth or lift its eye patch, and out spills a surprise: jelly beans or chocolate eyeballs, fed through tubes in back.