The staff at Grey Sloan Memorial Hospital (formerly Seattle Grace Hospital...and Seattle Grace Mercy West Hospital) is ever-changing. As Grey's Anatomy barrels along through its second decade on the air, it's only natural that the actors who make up its cast have changed. Yes, some characters have left Seattle and been replaced by new ones, but the longer the actors stay on the show, the more they change themselves (again, a totally natural thing—that's just how time works). Here's a look back at the Grey's Anatomy cast in their first seasons on the show and in their last. Keep scrolling to the very end to see how the long haul cast members—stars like Ellen Pompeo and Chandra Wilson, who have been with the show since season one—have changed in their 16 years and counting on the show.
In season 1, Sandra Oh's Cristina Yang was just an ambitious young intern, preparing to take over the cardiology department and become a world-renowned heart surgeon.
In season 10, Cristina left Seattle and is now kicking international ass as the Chief Medical Officer, and Director of Cardiothoracic Surgery at the Klausman Institute for Medical Research in Zurich. The character's graceful and open-ended exit is a testament to Oh's great relationship with Grey's Anatomy creator Shonda Rhimes, who is notorious for giving less-happy endings to characters when she doesn't get along with the actors who play them.
Heigl was a member of the OG Grey's Anatomy class of interns, playing Izzie Stevens, who paid her way through medical school by modeling.
Heigl left the series in season 6, following several rounds of highly-publicized drama behind the scenes. Part of why she left was (reportedly) to pursue her movie career, but that didn't go so well.
Rounding out the original group of interns at the heart of the show was T.R. Knight as George O'Malley.
Knight left the series in season 5 and his character, George, had a tragic-but-heroic exit.
Washington was one of Grey's Anatomy's original cast members, playing Head of Cardiothoracic Surgery, Preston Burke, in the show's earliest days.
Washington was at the center of Grey's Anatomy's first high-profile behind-the-scenes scandal, when he used a homophobic slur during a fight with Patrick Dempsey on set. The actor was written off the show in season 3 when he unceremoniously left Cristina Yang at the altar.
Although his time as a regular member of the Grey's cast ended in season 3, Washington made a guest appearance on the show in season 10 to give some closure to his character's relationship with Cristina when Sandra Oh left the show.
Patrick Dempsey joined the cast of Grey's Anatomy in Season 1 as Derek Shepherd (a.k.a. McDreamy), a neurosurgeon and Meredith Grey's love interest.
Derek and Meredith's love story was cut short in season 11 when Dempsey's character was abruptly killed off.
Kate Walsh made her first appearance as Derek Shepherd's ex-wife, Dr. Addison Montgomery in Grey's Anatomy season 1.
Walsh was a series regular throughout seasons 2 and 3 of Grey's Anatomy before leaving to head up her spin-off series, Private Practice.
Even though season 3 marked the end of Walsh's time as a series regular on Grey's, the actress continued to make guest appearances through season 8.
Sara Ramirez's Callie Torres started out as a recurring character (a senior orthopedic resident) in season 2 of Grey's Anatomy.
After a decade playing the hospital's Head of Orthopedic Surgery, Ramirez left in season 12.
Introduced in season 2 as a hot foil to Dempsey's McDreamy, Eric Dane played Mark Sloan (a.k.a. McSteamy), the plastic surgeon Derek's ex-wife, Addison, had an affair with.
Mark Sloan went through a lot of character growth during his seven seasons on Grey's Anatomy, and was solidly a fan favorite when Dane left the series for good in season 9.
Brooke Smith's Erica Hahn first appeared on Grey's Anatomy in season 2, when Izzie lied about Denny Duquette's condition to effectively steal a heart from another transplant patient who was being treated by Dr. Hahn.
Although she worked at Seattle Presbyterian when she was first introduced, Dr. Hahn eventually moved to Seattle Grace full-time and even started a romantic relationship with Callie Torres. However, when she learned the truth about Izzie's lie regarding Denny's condition, she quit abruptly, leaving the hospital (and the show) for good.
The first of Meredith Grey's secret siblings, Lexie Grey (played by Chyler Leigh) started her time at Seattle Grace in season 3.
Leigh ended her arc on Grey's in season 8, in one of the series' most iconic (and devastating) episodes ever, Flight, in which she dies in a plane crash.
Jessica Capshaw joined the cast of Grey's in season 5 as pediatric surgeon Arizona Robbins.
Capshaw stayed with the series until season 14, when Arizona moved to New York to reunite her family. Callie Torres, with whom she shared her daughter, Sofia, left a couple of seasons prior.
Sarah Drew joined the cast of Grey's Anatomy in season 6, as one of the residents brought over during the merger between Seattle Grace Hospital and Mercy West Hospital.
Drew left the series in season 14, after Shonda Rhimes took her character, April Kepner, through one of the twistiest (and at times divisive) arcs in the series' history.
Jason George started his run on Grey's Anatomy as a recurring character: Benjamin Warren, Miranda Bailey's love interest.
George's status in the cast has changed several times, from recurring to guest star to recurring again and finally to series regular. After a stint as a regular from season 12 to season 14, George dropped his Grey's commitment back to recurring character when his spin-off, Station 19 premiered.
George still occasionally makes appearances on Grey's. Here he is in season 16.
Kim Raver joined the Grey's cast for the first time in season 6, as Teddy Altman, a cardio surgeon and military veteran who shares a deep history with Cristina Yang's love interest Owen Hunt.