S1·E29 From Hopeless To Helpless, Part 2

Things looked bad for Polly, who's speeding down a car downward on a slope, and a wheel on the car even comes off. Fortunately, Underdog flies down and saves her just as the car falls off the cliff. After dealing with Polly, Underdog announces on the TV news that Riff Raff has the diamond. Enraged, Riff Raff thinks of a way to make sure Underdog doesn't bother him again. Later, Underdog finds signs that lead to Riff Raff's hideout, but in reality, he is lured inside a cave that starts eroding inside when Mooch blows it up. Meanwhile, Riff Raff is looking for an Underdog impersonator. He finds one named Tap Tap who is entirely perfect. Tap Tap and Riff Raff rob the bank, much to everyone's surprise when they see "Underdog" doing a crime.