Courage the Cowardly Dog Season 3 Episode 6 - Katz Under the Sea / Curtain of Cruelty Katz Under the Sea:Displeased by Eustace, Muriel takes Courage with her and they go on a submarine vacation. They realize too late that it is being run by one of their old enemies, Katz. Curtain of Cruelty:When a strange pink curtain is going through Nowhere making the citizens cruel and mean, Courage finds out that all of this is caused by Professor Mean, who is also cruel and unhappy, and wants everyone else to be cruel and unhappy too.