The Peter Potamus Show The sixth Hanna-Barbera syndicated cartoon after their departure from MGM starred Peter Potamus (a purple hippopotamus), and his traveling companion So-So (a monkey), who fly back and forth through time in a balloon participating in historic events. Whenever they get into serious enough trouble, as they do in every episode, Peter defeats his enemies with his trademark "Hippo Hurricane Hollar." Other cartoon shorts include, "Breezly and Sneely," and "Yippee, Yappee, and Yahooey."