Some info and a short description of this South Park episode on South Park Zone:
South Park - Simpsons Already Did It is the 86th episode of the Comedy Central series South Park. It originally aired on June 26, 2002.
Butters, in his evil alter-ego persona Professor Chaos, is trying to figure out a way to bring disarray to the town, but he discovers that all of his plots for destroying the world have been done before on the FOX animated sitcom The Simpsons, as Dougie in his evil alter-ego persona General Disarray, informs him that " SIMPSONS DID IT!" Butters abandons the idea.
Meanwhile, Cartman creates a miniature society of sea people in his aquarium and with a secret ingredient, the society will grow and evolve.
In the end, Cartman wonders, "Why can't societies live in peace?" - A pretty ironic way to end a South Park episode.
South Park Spoiler Alert!
(The complete plot for this South Park Episode)
Cartman shows Kyle, Stan, and Tweek an advertisement he found for "Sea People" which is ofcorse a parody of Sea-Monkeys. Cartman imagines them to be a race similar to mermaids who will "take me away from this goddamn planet full of hippies." He convinces everyone to chip in so they can buy them.Meanwhile, Butters, in his evil alter-ego persona Professor Chaos, is trying to figure out a way to bring disarray to the town. When he plots to block out the sun, his assistant, Dougie/General Disarray, informs him that it mirrors a plot of Mr. Burns's from The Simpsons and Butters abandons the idea.
Cartman soon begins to prepare for the Sea People, even making a sign to welcome them, but after placing them in the water, Stan reveals that they are simply brine shrimp. Cartman, in a fit of rage, begins to berate his friends, but stops after the group decides to place the shrimp in Ms. Choksondik's coffee. The scene then cuts to Ms. Choksondik's house, where an ambulance is taking away her corpse.
Butters decides to cut the head off of the town's central statue — which mirrors Bart Simpson's decapitation of Springfield's Jebediah Springfield statue. On the news report, the newscaster interprets Butters' vandalism as an homage to The Simpsons; the police are not investigating the crime because they want the statue to remain headless as a tribute.
Upon hearing that semen was discovered in the teacher's stomach, the boys conclude that they killed Ms. Choksondik with their "sea men". They go to the morgue to steal the evidence, fearful that they will "find the women too!" Butters devises increasingly outlandish schemes, but Dougie keeps pointing out that they have already been done on The Simpsons.
Eventually, Chef explains that there is a difference between "sea men/semen" and "Sea People", and that the brine shrimp did not kill their teacher. Cartman then discovers that when the semen they recovered has been added to the Sea People aquarium, it combines with the Brine Shrimp to create an intelligent race of actual sea people.
Trying to come up with an original plot, Butters watches every episode of The Simpsons before introducing his newest plan: build a machine that replaces the cherry centers of chocolate covered cherries with rancid mayonnaise. As Butters is about to use his device a Simpsons commercial announces that Bart will do exactly the same thing in that night's episode. Butters has a nervous breakdown and begins picturing the town in the animation style of The Simpsons.
At the Cartman household, the boys have bought more Sea People, a larger aquarium, and several gallons of semen. Their Sea-Ciety evolves into an Ancient Greek-esque civilization, and they begin worshipping Cartman.
Stan and Kyle invite Butters and others to see the aquarium. Butters then states that the Sea-Ciety plot is similar to that of the "Treehouse of Horror VII" short "The Genesis Tub". Though the boys agree with him, they also note that The Simpsons has done everything, so worrying about that is pointless. Chef also points out that they in turn borrowed their ideas from a classic Twilight Zone episode, "The Little People". Butters understands and everyone returns to their normal appearance. Butters then happily leaves, getting ready to wreak havoc once again. The Sea People on the other side of the aquarium begin worshipping Tweek, leading to a holy war. Seconds later they develop nuclear weapons and destroy themselves. While Kyle concludes war is inevitable, Cartman wonders, "Why can't societies live in peace?"