The sandwich monster was created by Scooby-Doo.
It's a giant, monstrous sandwich monster, with black and orange sclera eyes. Between the layers of individual sandwiches, there was filling such as sliced tomatoes, Swiss cheese, lettuce, salami, and bologna. It also has an olive on top of it's head. It has beige, tentacle-like arms and could form a wide mouth.
It intended to devour Shaggy Rogers. It was surprised, and possibly disappointed, when it was shrunken back down to size.
Scooby-Doo! (DC Comics)
While Shaggy made himself a towering sandwich, Scooby realized he was also hungry. He got a spell-book out of the cupboard, marked by Velma Dinkley as never to be opened, and recited a spell. Shaggy's sandwich morphed into a monster, and Shaggy ran from it in terror. Scooby recited some more magic words and the monster turned back into a sandwich. Chuckling to himself that it "works every time," Scooby ate the sandwich.