The gang gets ready for some serious shopping when they head to the Happy Valley Mega Mall. Daphne, Fred, Velma, and even Scooby-Doo and Shaggy want to check out the new store - Dr. Yuckenstein's Make-A-Monster Laboratory - where they can make their own customized monster dolls!
But - ruh-roh - a mega-sized monster has come to life and is scaring away all the customers! It's a monster of a mystery that only Scooby-Doo and Mystery, Inc. can solve!