George Clooney's Voice Was Unrecognizable As South Park's First Celebrity Guest Star

"South Park" creators Matt Stone and Trey Parker provide most of the voices on the show, including the main four characters, many of the supporting characters, and plenty of one-off or background characters. However, the series does occasionally utilize guest stars, and the very first was George Clooney — though it wasn't exactly a leading performance. Clooney played a gay dog named Sparky and only recorded barks and grunts as his "dialogue."

Clooney appeared in the fourth episode of the show's debut season, which aired on September 3, 1997. At the time, Clooney wasn't quite the A-list icon he is now. He'd starred in a few films — most notably, "From Dusk till Dawn" and "Batman & Robin" – but he was mainly a big deal for his leading role on one of the greatest medical dramas of all time, "ER." 

Clooney had been aware of "South Park" because he'd seen Parker and Stone's short film "The Spirit of Christmas." That video went viral in a pre-internet way, and major names in Hollywood were delighted by the raunchy short made with cut-up construction paper. Stone and Parker even credit Clooney with making tons of physical copies of the tape and sharing them around Los Angeles. "And then when the show got picked up, they called me, and the first thing they asked me to do was to play Sparky the Gay Dog," Clooney recalled in an interview with Variety. "And they recorded me, and they just had me bark."

George Clooney's episode, which deals with Stan learning that it's "okay to be gay" after he finds out that his dog is gay, was not the actor's only "South Park" appearance. In the 1999 movie "South Park: Bigger, Longer, and Uncut," Clooney makes a small cameo as the voice of a doctor who tries (and fails) to save Kenny's life. ("We accidentally replaced your heart with a baked potato. You have about three seconds to live.")

Guest spots like Clooney's are a relative rarity for "South Park," however. Unlike some animated shows — like "The Simpsons," which regularly gets celebrities to record guest voice roles, "South Park" uses them more sparingly. That said, there were a few guest stars in the early seasons, including Jay Leno, Jennifer Aniston, Malcolm McDowell, and a fair number of musicians like Robert Smith, Korn, Ozzy Osbourne, Meat Loaf, Primus, and Devo, most of whom appeared in the music-focused Season 2 episode "Chef Aid." In later seasons, there have been far fewer celebrity guests. Bill Hader, who wrote a few episodes, voices some characters in a handful of episodes in Seasons 15 through 19. Streamer PewDiePie appears as himself in Season 18, too, and the musician Sia voices Lorde in that same season. Josh Gad voices a main character in a Season 21 episode.

In Season 20, which aired in 2016, Elon Musk voiced himself in a few episodes. At a San Diego Comic-Con appearance that year, Trek Parker revealed he'd played Dungeons & Dragons with Musk. More recent episodes have taken some veiled shots at the controversial billionaire, however.