Question: What is the nickname of the fictional surgeon who is married to show's protagonist Meredith Grey?

Context articles: Richard Webber (disambiguation)
George O'Malley
Miranda Bailey
Cristina Yang
Sadie Harris
Meredith Grey
Mark Sloan (Grey's Anatomy)
Only Mama Knows (Grey's Anatomy)
Lexie Grey
Derek Shepherd

Richard Webber is a fictional surgeon on "Grey's Anatomy".
George O'Malley is a fictional character from the medical drama television series "Grey's Anatomy", which airs on the American Broadcasting Company (ABC) in the United States.
 The character was created by series producer Shonda Rhimes, and was portrayed by actor T. R. Knight from 2005 to 2009.
 Introduced as a surgical intern at the fictional Seattle Grace Hospital, O'Malley worked his way up to resident level, while his relationships with his colleagues Meredith Grey (Ellen Pompeo), Cristina Yang (Sandra Oh), Izzie Stevens (Katherine Heigl) and Alex Karev (Justin Chambers) formed a focal point of the series.
 O'Malley married Callie Torres (Sara Ramirez) whom he later separated with to pursue a relationship with Izzie Stevens.
 O'Malley also had entertained a romantic interest with Meredith Grey and Olivia Harper (Sarah Utterback).
Miranda Bailey, M.D. is a fictional character from the medical drama television series "Grey's Anatomy", which airs on ABC in the United States.
 The character was created by series producer Shonda Rhimes, and has been portrayed by actress Chandra Wilson since the show's inception in 2005.
 Introduced as a resident in general surgery at the fictional Seattle Grace Hospital, Bailey worked her way up to the attending physician level, and on September 24, 2015, was named the Chief of Surgery.
 Her relationship with the five surgical interns she was in charge of - Meredith Grey (Ellen Pompeo), Cristina Yang (Sandra Oh), Izzie Stevens (Katherine Heigl), George O'Malley (T.R. Knight) and Alex Karev (Justin Chambers) - formed a focal point at the beginning of the series.
Cristina Yang, M.D., Ph.D., is a fictional character from the medical drama television series "Grey's Anatomy", which has aired for over 12 years on the American Broadcasting Company (ABC) in the United States.
 The character was created by series producer Shonda Rhimes, and is portrayed by actress Sandra Oh.
 Introduced as a surgical intern at the fictional Seattle Grace Hospital, Yang worked her way up to resident level, eventually becoming a cardiothoracic surgical fellow, while her relationships with colleagues Meredith Grey (Ellen Pompeo), George O'Malley (T. R. Knight), Izzie Stevens (Katherine Heigl), and Alex Karev (Justin Chambers) formed a focal point of the series.
 Yang earlier in the series got engaged to Preston Burke (Isaiah Washington), in the past had a relationship with renowned surgeon and mentor Colin Marlow, and wed but later divorced Owen Hunt (Kevin McKidd).
Sadie Harris was a recurring fictional character from the American television medical drama "Grey's Anatomy", which airs on the American Broadcasting Company (ABC) in the United States.
 The character was created by series producer Shonda Rhimes and portrayed by actress Melissa George.
 Introduced as a surgical intern who has an old companionship with the series' protagonist Meredith Grey (Ellen Pompeo), she eventually forms a friendship with Lexie Grey (Chyler Leigh), and departs after it is revealed she cheated her way into the surgical program.
Meredith Grey, M.D. is a fictional character from the medical drama television series "Grey's Anatomy", which airs on the American Broadcasting Company (ABC) in the United States.
 The character was created by series' producer Shonda Rhimes, and is portrayed by actress Ellen Pompeo.
 Meredith is the series' protagonist, and was introduced as a surgical intern at the fictional Seattle Grace Hospital (later Seattle Grace-Mercy West, and afterwards Grey Sloan Memorial), eventually obtaining the position of a resident, and later the position of an attending, and in 2015, attaining the Chief of General Surgery position.
 As the daughter of world-renowned surgeon Ellis Grey, Meredith struggles with the everyday life of being in a competitive profession, maintaining the relationship with her one-night stand and eventual husband Derek Shepherd (deceased), her motherhood, and her friendships with her colleagues.
Mark Everett Sloan, M.D., F.A.C.S. is a fictional surgeon from the ABC medical drama television series "Grey's Anatomy", portrayed by Eric Dane.
 Dr. Sloan is an attending specializing in plastic surgery.
 Dr. Sloan earned the nickname “McSteamy” for his good looks by the female interns of Seattle Grace later Seattle Grace Mercy West Hospital.
 He was good friends with Dr. Derek Shepherd, a fellow physician at Seattle Grace, but was the catalyst for the end of Shepherd's marriage when Shepherd caught Sloan sleeping with his wife, Addison.
 Later, he pursues a 'forbidden' relationship with Dr. Lexie Grey, straining his relationship with Derek yet again.
 He reveals that he loves Lexie in episodes "Migration", "Flight", "Going, Going, Gone", and "Remember The Time" In the show's ninth season, he dies of injuries sustained in a jet plane crash that also injured or killed several of his colleagues from the hospital.
"Only Mama Knows" is the fourth episode of the eleventh season of the American television medical drama "Grey's Anatomy", and is the 224th episode overall.
 It aired on October 16, 2014 on ABC in the United States.
 The episode was written by Mark Driscoll and directed by Nicole Rubio.
 The episode focuses on the show's protagonist Meredith Grey's (Ellen Pompeo) past and troubled childhood and her relationship with her mother world-renowned surgeon Ellis Grey (Kate Burton) and Richard Webber (James Pickens Jr.) while she struggles in her marriage with Derek Shepherd (Patrick Dempsey).
 On its initial airing it was watched by 8.43 million viewers and received universal acclaim from television critics with many calling it one of the best episodes of the entire series.
Alexandra Caroline "Lexie" Grey, M.D. is a fictional character from the medical drama television series "Grey's Anatomy", which airs on ABC in the United States.
 The character was created by series' producer Shonda Rhimes and was portrayed by actress Chyler Leigh from the third through eighth seasons.
 She was introduced as a surgical intern in season three.
 Serving as Meredith Grey (Ellen Pompeo)'s half sister, she transferred to the fictional Seattle Grace Hospital, after her mother's sudden death.
 Eventually named a surgical resident, the character was originally contracted to appear for a multi-episode story arc, but received star billing in the fourth season.
Derek Christopher Shepherd, M.D., also referred to as "McDreamy", is a fictional surgeon from the ABC medical drama "Grey's Anatomy", portrayed by actor Patrick Dempsey.
 He made his first appearance during "A Hard Day's Night", which was broadcast on March 27, 2005.