Kate is having a big birthday party and she invites everyone from her class including Lizzie, Miranda and Gordo. But Lizzie and Miranda's parents refuse to let them go to the party as there would be no adults around (and Kate's cousin Amy (Haylie Duff) doesn't make good chaperone material). So, Lizzie, Miranda and Gordo lie at their homes and go to the party anyway. But the party goes horribly wrong and Lizzie calls her mother for help. Eventually, all three are grounded for lying and going to the party anyway. Meanwhile, Matt and Sam are selected to star in a commercial for Cardio Punch Sports Drink.