Pluto was Cleo's pet fish, he died in the episode "Dangerous Waters." Cleo was very upset over his death and held a sermon for Pluto on her jetty, and dropped him back into the ocean. Rikki didn't get the caring and tried to replace Pluto with a freshwater fish. This led Rikki to find new saltwater fish from the ocean for Cleo, to show that although she doesn't understand the affection, she still understands that Cleo cares for her fish. Cleo named her new fish Hotstuff in Rikki's honor.