Even though Grey's Anatomy has been on the air for 16 years, there are only 3 original cast members that still grace viewers' screens every Thursday night. The rest of the cast is made up of characters that were introduced after the first season, which only consisted of nine episodes.
Each season has brought new people into the Grey's universe, whether they were previously mentioned as family members or were totally new faces at the hospital. Given the high turnover rate with doctors at Grey-Sloan Memorial, it's no surprise that they'd need to get some replacement surgeons year after year.
Atticus Lincoln
Head of orthopedic surgery and cancer survivor Atticus 'Link' Lincoln started working at Grey Sloan Memorial Hospital in Season 15 of the series.
Link's close friendship with Jo Wilson and romantic relationship with fan-favorite Amelia Shepherd made him liked by viewers. Fans were thrilled when it was revealed that he was in fact the father of Amelia's baby, and not her ex-husband Owen Hunt. Link hasn't been on the show long, but his ability to bring Amelia long-awaited happiness made him a perfect and necessary addition.
Maggie Pierce
Season 10 introduced a new family member for Meredith, a half-sister named Maggie Pierce. Maggie was revealed to be the daughter of Ellis Grey and Richard Webber, who was put up for adoption when she was a baby.
Maggie's arrival at Grey-Sloan gave Meredith a chance to have a re-do at a close relationship with a sister following the death of her other half-sister, Lexie. Maggie also propelled Richard's story by being his only child. Maggie's intellect and passion for surgery allow for her to have her own fun storylines, and add to those of the original cast members.
Arizona Robbins
Following the departure of Addison Montgomery, Grey's introduced a new pediatric surgeon in Season 5. Arizona Robbins arrived in wheelie shoes with bright blonde hair, immediately setting her apart from the other doctors at Seattle Grace.
Arizona's bubbly demeanor and passion for working with children made her fun to watch and allowed her to bond with Alex Karev over pediatrics. Her relationship and eventual marriage to Callie Torres was a sweet love story, though their eventual divorce was disappointing to viewers. Arizona was a joy to watch, and a Peds surgeon the hospital desperately needed.
Jo Wilson
Season 9 introduced a new class of interns, one of which being the one and only Jo Wilson, played by English actress Camila Luddington.
The introduction of Jo's character gave Alex Karev the epic love story he always deserved and allowed Meredith to bond with someone who resembled her as an intern. Meredith and Jo both had different traumatic pasts and were eventually able to bond and help each other. Jo and Alex's love story may be over, but Jo's character still deserves one of her own.
April Kepner
Season 6 introduced a handful of new residents as Seattle Grace merged with Mercy West. One of those new additions was the over-eager and slightly annoying April Kepner.
April was fired shortly after her arrival but was re-hired when Derek became Chief of Surgery. Her quirks began to subside as she got more comfortable in her new space, and the relationship she formed with fellow Mercy West alumni Jackson Avery was a romance that fans couldn't help but root for, even after her character left the show in Season 14.
Ben Warren
Following a difficult divorce, Miranda Bailey found herself attracted to the flirty anesthesiologist from Mercy West in Season 6. Ben Warren gave Bailey the love that she always deserved, even when she couldn't fully realize that she deserved it.
Additionally, his career switch-ups throughout the show - from anesthesiologist to surgical resident to firefighter - was a realistic portrayal of anyone without a straightforward career path.
Jackson Avery
Another Mercy-West resident that luckily wasn't dealt a tragic fate at the end of Season 6 was Jackson Avery. Jackson began his tenure at Seattle Grace as an outsider, but eventually became a likable character and one of the longest-lasting Grey's has seen.
His soft-spoken nature and friendship-turned-marriage with fellow Mercy Wester April Kepner gave him a plethora of interesting storylines, and the introduction of his mother, Catherine, gave a deeper insight into his family life.
Amelia Shepherd
Amelia Shepherd first appeared on the spinoff Private Practice but ended up crossing over to Grey's Anatomy as a series regular beginning in Season 11.
The addition of Amelia to the show as a main cast member allowed Meredith to gain another sister, one she desperately needed after the departure of Cristina Yang and the death of her husband Derek at the end of Season 11. Amelia's story was allowed to continue on Grey's after the end of Private Practice, hopefully giving her character a truly happy ending she deserves.
Mark Sloan
In the latter half of Season 2, Derek's ex-best friend and Addison's former lover Mark Sloan arrives at Seattle Grace. He wreaks havoc as the Shepherds are in the midst of rebuilding their already broken marriage.
When Mark eventually took the job of Head of Plastic Surgery at Seattle Grace, he formed a close friendship with Callie Torres and an adorable relationship with Lexie Grey. Mark's bromance with Plastics Posse member Jackson Avery in his later seasons displayed his character growth, and it was heartbreaking to watch him say goodbye to those he loved after the horrific plane crash.
Lexie Grey
Derek Shepherd met a girl at a bar in the first episode of Season 1 and the last episode of Season 3. His second time around, he was introduced to Meredith's half-sister Lexie, unbeknownst to him.
Lexie's arrival in Seattle allowed for Meredith to finally have a non-toxic familial relationship, even if she initially resisted Little Grey's presence. During her time on the show, Lexie brought a sense of naivety and innocence and was on track to be an incredible neurosurgeon like her brother-in-law.