MTVYou didn't know Lily Collins appeared on The Hills?
The show turned Lauren Conrad and co. into stars, but during its six-season run, it also featured a number of celebrities who were already established. In blink-and-you'll-miss-it moments, the MTV series featured everyone from Hilary Duff to Jason Lee (really!) hanging out at the hottest parties in Hollywood. Others, like Lady Gaga and Derek Theler, made more prominent cameos.
In honor of the reality show's 10th anniversary, Lauren shared behind-the-scenes stories with longtime fans in MTV's The Hills: That Was Then, This Is Now special. The retrospective, which aired Tuesday, also included a never-before-seen scene that showed Kim Kardashian admiring the fish tank in Heidi Montag and Spencer Pratt's new apartment. "We're the only people in America to have jellyfish," Heidi bragged. During the party, Kim was seen speaking to her then-stepbrother, Brody Jenner, about her upcoming trip to Las Vegas to attend the MTV VMAs. Kim and her family would go on to star in their own popular reality show, E!'s Keeping Up With the Kardashians, but she wasn't the only future reality star to pop up on the Laguna Beach spinoff. Vanderpump Rules' Tom Sandoval modeled in season 1, while Scheana Shay—a friend of "Stacie the Bartender"—appeared in several episodes during the show's penultimate season.
To see which other celebrities appeared on The Hills, check out the gallery.