When Miss Beazley discovers Dilton's newest formula in the school fridge, she accidentally mistakes it for the secret ingredient to her tapioca pudding -- and once it's a part of the recipe, the pudding grows, and grows, until it's large enough to devour everything in its way! With Miss Beazley, Miss Grundy, and Betty in the beast's belly, it's up to Archie and Reggie to set aside their rivalry in order to work together to stop the pudding's rampage.