Lexie Grey (Chyler Leigh) appears for the first time in Season 3 as a smart but socially awkward surgical intern who is about to start work at Seattle Grace Hospital. Her closest relatives are her half-sister, surgical resident Meredith Grey (Ellen Pompeo), and her alcoholic father, Thatcher Grey (Jeff Perry). Lexie's most serious romantic partners have been Dr. Mark Sloan (Eric Dane) and surgical resident Alex Karev (Justin Chambers).
When Lexie arrives at Seattle Grace, she is eager to become close to Meredith. Although she is hurt by Meredith's frequent rejections, Lexie doesn't give up. Her persistence eventually wins over her sister, and they become close friends. Romantically, Lexie and Alex have a brief "no strings attached" sexual relationship. Lexie then becomes interested in George O'Malley (T.R. Knight), who remains oblivious to her feelings. In Season 5, Lexie turns her attentions to plastic surgeon Mark Sloan. Despite their age difference and his reputation for promiscuity, they become involved.
Major events in Lexie's life include George's death, making it through a severe staff reduction at Seattle Grace, and convincing Meredith to donate part of her liver to Thatcher. Lexie's relationship with Mark then falls apart when Mark makes it clear that he will choose his teenage daughter, Sloan Riley (Leven Rambin), over her. Lexie leaves Mark and soon rekindles her sexual relationship with Alex. Meanwhile, Mark decides he wants Lexie back. In the season finale, a crazed gunman opens fire in Seattle Grace and almost shoots her.
At the end of Season 6, Lexie remains torn between Alex and Mark. She is also traumatized because of nearly being killed in her workplace. Lexie's character was originally added to "Grey's Anatomy" to provide the basis for a new core group of younger characters.
"I respect you. As a man. As a surgeon, as a teacher. I respect you. So... teach me."
"I forgive you for treating me like crap, and I forgive you for letting your friend treat me like crap."