Mrs Creecher uses the school's allotment to hold Class 3C's 'Biggest Veg' competition. Determined to outshine Walter, Dennis will do anything to grow the biggest veg. Little does he know that JJ's gran's special potion, when mixed with Walter's dad's V-V plant food, will transform their plants into giant living, walking, groaning veggies. They turn to Paul the Potato to help them 'smoothie' out the situation!