Alas, the kit took forever to dry apples, and the craft supplies included ran out quickly, especially if you were the OCD-type kid I was and had to design complete outfits and accessories for your apple heads. But, with my sister's help, I later discovered that you could actually shrink apple heads in the oven!
For a quick and dirty lesson, check out this amusing article at x-entertainment. It may be a little TOO quick and dirty - I'd like to think my childhood creations were more impressive, but it might be just the thing for a drunken night with friends.
And while you're there, check out the article on Pet Costumes featuring a Mingo look-alike (only... less... husky). Great funny stuff on that site in general.