Mark Sloan found his Grey's Anatomy person in Lexie Gray. Plastic surgeon Mark (played by Eric Dane) joined Grey's in 2006's season 2 as Derek Shepherd's (Patrick Dempsey) best friend who had an affair with his then-wife. Derek was married to Addison Montgomery (Kate Walsh) ahead of the show before he found love with Meredith Grey (Ellen Pompeo) by the pilot. By the time Mark joined the Seattle Grace Hospital team, he was in no rush to settle down and often hooked up with a bevy of respective interns and nurses. He secretly had sex with Meredith's half-sister Lexie (Chyler Leigh) by season 5.