As Grey's Anatomy Season 15 comes to a close, we can't help but remember those stars who helped build this show into what it is today.
Grey's Anatomy has been a stepping stone for those new to the business, as well as a place for name brand actors to make an exciting appearance.
The list of guest stars is extensive, and thanks to Shonda we're lucky to enjoy limitless Grade-A acting.
Related: 27 Celebrities You Probably Forgot Were On Grey's Anatomy
Some of these actors you may recognize from your favorite childhood movies, top rated TV shows, or small indie films. Others may be unrecognizable due to the incredible makeup on the show.
Leave us any comments below with any we may have missed. But don't forget to check out this slideshow's prequel for a few more familiar faces.
If you want to see how they all look in action, you can watch Grey's Anatomy online via TV Fanatic.
Dylan Minnette is such a baby during his Grey's Anatomy Season 4 Episode 5 debut. His character, Ryan, trick-or-treats for ears from Mark Sloan. He's now the star of the Netflix original series 13 Reasons Why.
Known for his role on the classic Veronica Mars, Teddy Dunn made an appearance on Grey's Anatomy Season 2 Episode 20 as a hockey player who cuts his off his own finger in an attempt to play and impress the scouts.
Alex Karev's patient turned love interest, Rebecca Pope was portrayed by Elizabeth Weaser. Rebecca was brought in after the major ferry crash that devastated the city on Grey's Anatomy Season 3 Episode 15. Perhaps you've seen Weaser in the Netflix original series The Haunting or way back when as Edward Cullen's mom Esme Cullens.
Hilarie Burton came onto Grey's Anatomy Season 9 as Lauren Boswell a specialized surgeon who assists one of Arizona's cases and eventually becomes the woman Arizona cheats with. Hilarie is most notably known for her portrayal as Peyton Sawyer on One Tree Hill.
Martha Plimpton from the TV show Raising Hope portrayed Pam Michaelson, a mother on Grey's Anatomy Season 6 Episode 1, whose son was suffering from pain unrelated to his original treatment. Her insurance wouldn't cover the treatment so she was sent away, but she fought hard for her son and was able to get to the root of his diagnosis.
Millie Bobby Brown
Millie Bobby Brown has gained recent traction with her breakout role as Eleven from Stranger Things. In her small guest role as Ruby on Grey's Anatomy Season 11 Episode 15, she saved her mom's life after being instructed over the phone by doctors how to perform a thoracotomy.