Spookyfish

"Spookyfish" is the fifteenth episode of the second season of the American animated television series "South Park". It is the 28th episode of the series overall. It first aired on Comedy Central in the United States on October 28, 1998. Trey Parker wrote the episode.
Plot.
In the episode, Stan's mother's Aunt Flo comes to stay. She gives Stan a goldfish as a present. But the goldfish is evil and kills people. Stan's mother thinks it is Stan who has killed the people. She hides the bodies.
Meanwhile, Cartman's double from another universe appears. He is from an opposite universe where mean people are nice and nice people are mean, so this visiting Cartman is nice. He helps the boys with their pumpkin carving contest. He tries to help Stan and his friends defeat the evil fish. All the characters from the evil universe have goatee beards, a reference to the " episode of ".