It's funny, not brutal. The alien visitors make a stop in South Park. In search of intelligent life, they implant a satellite in Cartman to find it. They apparently don't find it in Cartman, nor in the other South Park folks. They discover it in the local cows.
South Park covers the genetic engineering controversy in a different light.
A four-bottomed monkey, a hybrid of Swiss cheese and a beard and a psychotic Sam clone are just a few of the products we see. When Stan, the typically mild little boy, is cloned into a crazed, mammoth-headed mutant, the dangers of gene splicing are shown. It's every kid's dream. Shelly, Stan's older sister and worst nightmare, adds a little spice to South Park. Cartman's mom is a regular supermom, with cookies in the oven and cheesy poofs on the table at all times.