"Cartman Gets an Anal Probe" is the series premiere of the American animated television series South Park. It originally aired on Comedy Central in the United States on August 13, 1997. The episode introduces child protagonists Eric Cartman, Kyle Broflovski, Stanley "Stan" Marsh and Kenneth "Kenny" McCormick, who attempt to rescue Kyle's adopted brother Ike from being abducted by aliens.

Part of a reaction to the culture wars of the 1990s in the United States, South Park is deliberately offensive. Much of the show's humor, and of "Cartman Gets an Anal Probe", arises from the juxtaposition of the seeming innocence of childhood and the violent, crude behavior exhibited by the main characters. At the time of the writing of the episode, South Park creators Trey Parker and Matt Stone did not yet have a series contract with Comedy Central. Short on money, they animated the episode using a paper-cutout stop-motion technique, similar to the short films that were the precursors to the series. "Cartman Gets an Anal Probe" remains the only South Park episode animated largely without the use of computer technology.

Despite South Park eventually rising to immense popularity and acclaim, initial reviews of the pilot were generally negative; critics singled out the gratuitous obscenity of the show for particular scorn. Regarding the amount of obscenity in the episode, Parker later commented that they felt "pressure" to live up to the earlier shorts which first made the duo popular. Critics also compared South Park unfavorably with what they felt were more complex, nuanced animated shows, such as The Simpsons and Beavis and Butt-Head.

As Kyle Broflovski, Stan Marsh, Kenny McCormick, and Eric Cartman wait for the school bus, Kyle's brother, Ike, tries to follow Kyle to school. Kyle tells Ike he cannot come to school with him. Cartman tells the boys about a dream he had the previous night about being abducted by aliens. The others try to convince him the events did happen and that the aliens are called "visitors", but Cartman refuses to believe them. Chef pulls up in his car and asks if the boys saw the alien spaceship the previous evening, confirming Cartman's "dream", and relays stories of alien anal probes (which Cartman denies he experienced throughout the episode). After Chef leaves, the school bus picks up the boys, and (looking out the back window) they watch in horror as the visitors abduct Ike. Kyle spends the rest of the episode attempting to rescue him.

At school, Cartman begins farting fire, and Kyle unsuccessfully tries to convince their teacher, Mr. Garrison, to excuse him from class to find his brother. When Chef learns that Kyle's brother was abducted and sees a machine emerge from Cartman's anus, he helps the boys escape from school by pulling the fire alarm. Once outside, Cartman reiterates that his abduction was only a dream, when suddenly he is hit by a beam that inexplicably causes him to begin singing and dancing to "I Love to Singa". Soon afterward, a spaceship appears. Kyle throws a stone and the spaceship fires back, propelling Kenny into the road. As he gets back up, he is trampled over by a herd of cows, but survives. A police car then runs Kenny over and kills him.

Stan and Kyle meet Wendy Testaburger at Stark's Pond, where she suggests using the machine lodged inside Cartman to contact the visitors. To lure them back, the children tie Cartman to a tree and, the next time he flatulates, a massive satellite dish emerges from his anus. The alien spaceship arrives and Ike jumps to safety once Kyle asks him to do an impression of "David Caruso's career". In the meantime, the visitors communicate with the cows in the area, having found them to be the most intelligent species on the planet. Cartman is again abducted by the aliens, but is returned to the bus stop the following day with pinkeye.

The origins of South Park date back to 1992, when Trey Parker and Matt Stone, then students at the University of Colorado, created a Christmas-related animated short commonly known as "Jesus vs. Frosty". The low-budget, crudely made animation featured prototypes for the main characters of South Park. Fox Broadcasting Company executive Brian Graden saw the film, and in 1995, he commissioned Parker and Stone to create a second short that he could send to his friends as a video Christmas card. Titled The Spirit of Christmas (also known as "Jesus vs. Santa"), the short more closely resembled the style of the later series. The video was popular and widely shared, both by duplication and over the Internet.

After the shorts began to generate interest for a possible television series, Fox hired Parker and Stone to develop a concept based on the shorts for the network. The duo conceived the series set in the Colorado town of South Park and revolving around the child characters Stan, Kyle, Kenny, and Cartman as main protagonists, and included a talking stool character named Mr. Hankey as one of the minor supporting characters. The inclusion of Mr. Hankey led to disputes between Fox and Parker and Stone, and further disagreements caused the duo to part ways with the network. Later, Comedy Central expressed interests in the series, and Parker and Stone created a pilot episode for the network.