Marc Jacobs had a blink-and-you'll-miss-it cameo in Season 3 of The Hills, when Lauren was sent to New York City to assist with Fashion Week.
While Lauren was in at the Marc Jacobs offices, the famed designer ducked his head in to greet LC, and that was... kind of it. We guess someone as successful as Marc has a right to remain an enigma.
It's difficult to remember a time when Kim Kardashian wasn't famous. However, back when she was known for being an L.A. It-girl and Paris Hilton's best friend, she made an appearance on The Hills at one of Heidi and Spencer's many apartment parties. While her scenes were cut from the show, the memory lives on in recently released stills and video from MTV, showing Kim socialising with Heidi Montag and step-brother Brody Jenner.
Many years after the appearance, Spencer Pratt revealed that before Kim was everywhere, Kris Jenner actually asked Spencer if he'd be Kim's manager. How times change.
Emily Weiss, the brains behind cult beauty brand Glossier, was simply a Teen Vogue intern when she appeared on The Hills in 2007 on a three-episode arc, opposite Lauren and Whitney.
Back then, we remember being charmed by Emily's pleasant demeanor and extremely hard work ethic, and it seems not much has changed at all. However, with her company well on the way to being a global beauty empire, Weiss's role on the show is something that'll most likely surprise more and more people as she ascends in success.
Before Gaga was as entrenched in fashion and culture as Madonna, she appeared on The Hills in 2008 - and actually got in a bit of a kerfuffle.
While being assisted backstage by LC and Whitney at a performance at AREA Nightclub in L.A., Gaga suffered a near-wardrobe malfunction before having to perform, with a latex suit that wouldn't close - but the girls managed to save the day, and luckily, the entire escapade was caught on film.
That's right - before Gaga was being dressed by McQueen and Versace, she was in the trusty hands of Lauren Conrad and Whitney Port. A slight switch-up, no?
André Leon Talley
American Vogue contributing editor André Leon Talley coincidentally appeared in probably one of the most dramatic episodes of the entire show. During a live TV appearance featuring Talley that was documented for The Hills, Talley witnessed Whitney Port fall down a flight of stairs while modelling Hilary Swank's legendary blue Guy Laroche dress - not just for The Hills cameras to see, but the entire country live on Good Morning America.
Nevertheless, André brought light to the situation with his effervescence, and it's probably one of the most unforgettable fashion cameos of them all.
Okay, so we know Olivia Palermo's spot on MTV's spin-off The City basically launched her career, but her fashion powerhouse status far exceeds her antics on the short-lived show, which ran for two seasons from 2008 to 2010.
Her style has obviously undergone quite the makeover too; pictured on the left is Palermo during her stint on the show, and on the right in head-to-toe Miu Miu at the label's Spring/Summer 2018 show in Paris. Nevertheless, Palermo remains one of the most stylish reality TV stars in history.