S1·E24 The Bubbleheads, Part 1

Far beneath the sea in the kingdom of Maldemare, the Empress scorns the Emperor for not taking over the surface dwellers. He informs her that he has 3 of his top scientist working on the problem. The first demonstrates his volcano machine which erupts, but Underdog quickly puts out its spew. His failure provokes the Empress to have him thrown into the giant clam. The second scientist demonstrates an earthquake machine, which, again is defeated by Underdog. He too is thrown to the giant clam. The final scientist has the Emperor and Empress observe his Tidal Wave Machine, which begins to churn under the sea, gradually and eventually causing a giant tidal wave. The Empress instructs him to turn it on. And they wait for the needle to reach the tidal wave point.