Trends on TikTok are usually connected to something in pop culture. Lately, many users have been using a sound that says "Kill John Lennon," the famous guitarist, vocalist, and founder of the iconic band The Beatles. But how can you kill someone who's already passed on?Although this TikTok trend may sound somewhat concerning at first, it actually has a pretty hilarious backstory that fans of a certain iconic TV show will love. Here's where the audio comes from and why people are using it with their pets.What is the 'Kill John Lennon' TikTok trend?Because of the name, you might think the trend is about John Lennon, but it actually has virtually nothing to do with the musician and is mainly about TikTokers' pets. They film their furry friends as an audio saying "Kill John Lennon" plays. After the phrase is said, an ominous piano plays and, a lot of times, these animals look ready for the hunt. \n\nSpoilers for South Park season 14 episode 2 below!Originally, this audio comes from an episode of South Park. During Season 14, Episode 2 of the show, titled, "The Tale of Scrotie McBoogerballs," Stan, Kyle, Cartman, and Kenny write a book of the same title after reading The Catcher in the Rye in class. They believe the best-selling title isn't offensive enough and write a book of their own that they think truly pushes the envelope.To avoid getting in trouble, the four of them convince Butters that he wrote The Tale of Scrotie McBoogerballs while he was sleepwalking. Butters believes them, because after he reads The Catcher in the Rye, he wants to kill a bunch of people who have already passed, including John Lennon. Under some kind of trance, it's him who's saying "Kill John Lennon" in the TikTok audio.In this TikTok trend, pet owners are using the "Kill John Lennon" audio as a way to see how evil their furry friends are. If they hear the audio and look ready to hunt someone down, they are obviously an assassin in disguise. Some users are calling their pets secret sleeper agents.Here's where you can watch 'South Park.'Over the years, South Park has gained a dedicated following. It's been on the air since 1997, and while many of its fans have grown up with the show, there are also tons of people who are discovering it on a regular basis. Over the years, it's been featured on a number of different streaming platforms.Currently, you can watch all 25 seasons of South Park on HBO Max. The movies South Park: Bigger, Longer & Uncut, South Park: Post COVID, and South Park: Post COVID: The Return of COVID are all on Paramount Plus. There are also free episodes and clips on the show's website, and you can watch the show as it airs on Comedy Central.