5 Things to Know About 'Dancing with the Stars' ' Mischa Barton

When Mischa Barton joined the cast of Dancing with the Stars, O.C. fans across the world toasted the news of her return to TV with a mojito (not made by Oliver, of course).

But in case you weren’t watching soapy teen dramas in the early aughts, here are five things to know about Barton, 30, before she hits the floor Monday.

1. She was a child actress.
Haley Joel Osment gets all the credit, but Barton was a real scene-stealer in 1999’s M. Night Shyamalan thriller The Sixth Sense as the little ghost girl vomiting all over herself. (As it turns out, her on-screen mother had poisoned her to death in a case of Munchausen by proxy.)

2. She’s actually British.

Barton’s mother is Irish, her father is English and she was born in London, where she lived until she was 5 years old. She became a naturalized U.S. citizen in 2006.

3. She shot to stardom on The O.C.
Barton became an overnight sensation in 2003 by playing poor little rich girl Marissa Cooper on the Fox show about the scandals and secrets in California’s elite Newport Beach community. But she left the show after season 3, with her character dying tragically in a car wreck to a haunting “Hallelujah” cover by (who else?) Imogen Heap. The O.C. only lasted one more year.

4. She struggled in the spotlight.

Barton made headlines for hanging out with party girls like Paris Hilton and was arrested for a DUI in 2007. Two years later, she was placed under a 5150 psychiatric hold, and she’s now estranged from her mother and former manager Nuala, whom she’s suing for allegedly stealing her money. Still, she opened up to PEOPLE in 2013 cover story about her “full-on breakdown.” “It was a train I could not get off of,” she said. “When you’re young, you can do it, but after a while, it’s going to come crashing down on you.”

5. Now, she’s ready to rumba.

Barton told PEOPLE she’s excited to push her limits and “learn something” about herself on DWTS – and she’s got past champion Rumer Willis, who she met through dad Bruce Willis while filming The Sixth Sense, in her corner. “She told me, ‘You are going to have the best time. It’s like family,’ ” Barton said. “And that’s exactly what it’s been like so far.”

Season 22 of Dancing with the Stars premieres Monday at 8 p.m. ET on ABC.