How You Know Her: McKellar, 39, gained fame as a child actress playing Winnie Cooper on The Wonder Years, but now is known for writing math books aimed at middle school and high school girls. She also had a recurring role as Elsie Snuffin on The West Wing in the early 2000s.
Partner: Valentin Chmerkovskiy
2 of 12 Craig Sjodin/ABC
Candace Cameron Bure
How You Know Her: Bure is best known for playing eldest daughter D.J. Tanner on Full House. She's also appeared as a commentator on VH1's I Love the '80s and published her second book, Balancing It All: My Story of Juggling Priorities and Purpose, earlier this year.
Partner: Mark Ballas
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Billy Dee Williams
How You Know Him: Williams, a stage and screen veteran, gained fame as the star of several blaxploitation films in the 1970s. The 76-year-old will also reprise the role of Lando Calrissian in the upcoming Star Wars Episode VII.
Partner: Emma Slater
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Charlie White
How You Know Him: Off of the ice, into the ballroom! Charlie White, 26, and his ice dancing partner Meryl Davis (who's also competing on DWTS this season) just took gold in the 2014 Winter Olympics.
Partner: Sharna Burgess
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Amy Purdy
How You Know Her: Purdy, a double amputee, is a snowboarder on the U.S. Paralympic team. She was also a contestant on The Amazing Race in 2012.
Partner: Derek Hough
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Cody Simpson
How You Know Him: The 17-year-old heartthrob is a pop singer from Australia who supported Justin Bieber on several European dates of Bieber's "Believe" tour. He's also appeared on Cupcake Wars, Punk'd and Extreme Makeover: Home Edition.
Partner: Witney Carson
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Diana Nyad
How You Know Her: Nyad, 64, set a record last summer when she became the first person to swim from Cuba to Florida without the aid of a shark cage, on her fifth attempt.
Partner: Henry Byalikov
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Drew Carey
How You Know Him: The former star of his own sitcom, The Drew Carey Show, Carey went on to host Whose Line Is It Anyway? and is currently at the helm of The Price Is Right. Carey, 55, also hosted the Miss Universe pageant in 2013.
Partner: Cheryl Burke
9 of 12 Craig Sjodin/ABC
James Maslow
How You Know Him: Maslow, 23, plays James Diamond on Nickelodeon's sitcom Big Time Rush and also is a member of the boy band the sitcom follows.
Partner: Peta Murgatroyd
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Meryl Davis
How You Know Her: On the heels of their gold medal win at the Sochi Olympics, 27-year-old Davis and her ice dancing partner Charlie White will find themselves competing against each other rather than on the same side during Season 18 of Dancing. One of their Olympic routines was choreographed by DWTS mainstay Derek Hough.
Partner: Maksim Chmerkovskiy
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Nene Leakes
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Sean Avery
How You Know Him: Avery is a former NHL player who most recently played for the New York Rangers before announcing his retirement on Watch What Happens Live in 2012. The 33-year-old now works in advertising in New York City, and has appeared on Project Runway: All-Stars and Fashion Police.
Partner: Karina Smirnoff