The 32-year-old actress took to Instagram on Friday to share the first pic of herself alongside Hills stars Audrina Patridge and Stephanie Pratt. Barton confirmed she would be joining the MTV's revival series, The Hills: New Beginnings, on Oct. 3, which just so happens to be Mean Girls Day. The actress playfully referenced the cult classic in her caption on Friday.
"On Wednesdays we wear whatever we want... and you can totally sit with us 💋," Barton wrote.
Pratt shared the same snap, which she captioned, "Hanging out in #TheHills 💫@audrinapatridge @mischamazing ✨.
While Barton never appeared on the original Hills or Laguna Beach: The Real Orange County, she explained on Instagram last week that her former role on The O.C. made her the perfect choice to join the new show.
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"The secret’s out... I’m joining the cast of The Hills. When MTV approached me with the chance to be a part of the reality show that was inspired by The O.C.," she said. "It felt like the perfect opportunity for an irresistibly inviting new chapter."
ET previously confirmed that Brody Jenner and his wife, Kaitlynn Carter Jenner, were joining the reboot. Patridge and Pratt -- alongside her brother, Spencer Pratt, and Heidi Montag -- will also be returning for the show, with Justin Bobby, Jason Wahler, Jennifer Delgado, Ashley Wahler and Whitney Port.
The Hills: New Beginnings is slated to premiere in 2019. See more in the video below.