"It's a quick draw contest, Slim. First you have to be able to pick out which are innocents and which are the true jerks, then you draw your wand and zap them. The trick is that if you change an innocent, he or she will become a five inch amphibian (ten second penalty). If you get a real jerk, there's no change in appearance, they just start saying "ribbet."
She smiles and helps to put away the cheese.