Grey's Anatomy boasts one of the most talented casts on TV, so it's easy to imagine the fantastic actors playing all sorts of roles in other projects — in fact, most of them have. What we can't imagine is the cast switching parts within the show itself, because everyone seems to have been placed in the perfect part for them. But if you dig into the actors' casting stories, you quickly learn that Grey Sloan Memorial could have looked very different if everyone had landed the roles they originally auditioned for.

We've rounded up our favorite stories of Grey's cast members who originally auditioned for a different role on the show than the one they landed.

Isaiah Washington. Many Grey's fans know that Isaiah Washington was originally up for the role of Derek Shepherd. We can't imagine anyone but Patrick Dempsey playing McDreamy, and after Isaiah's strained departure from the show, we're especially glad he wasn't cast as the man Meredith is meant to be with.

Sandra Oh. Sandra Oh first auditioned for the role of Bailey. "Thank god I did not get that part!" she joked at a Paley Center panel. "Can you imagine not having [Chandra Wilson]? Forget it!" Not to mention, we can't imagine anyone but Sandra as Cristina. Fortunately, she felt the same way — after seeing the role of Cristina, she asked for that part instead.

Jessica Capshaw. In Jessica Capshaw's first attempt to land a role on Grey's, she auditioned for the part of Nurse Rose. She didn't get the gig, so a year later she tried out for another part. No, not Arizona — Sadie Harris (Melissa Gorga's character). She didn't get that, either. Finally, a month later she was offered Arizona. See, it all works out in the end!

Sarah Drew. Sarah Drew already knew Shonda Rhimes from Private Practice, so she didn't actually have to audition for Grey's. However, she did almost end up on the hospital drama in a guest role that "really would have been gone after two episodes." Fortunately for her, she had a scheduling conflict with that part, so instead Shonda gave her April, which evolved from a short guest stint into a full time role. Lucky Sarah!

Tessa Ferrer. While we don't know who Tessa tried for before she landed Leah, she tells TV Guide that she "auditioned a couple of times for different roles" on the show.

Sources: IMDB, The Paley Center for Media, TV Guide

Rebecca Martin is an Associate Editor at Wetpaint Entertainment and our resident Game of Thrones, Breaking Bad, and genre TV expert. Follow her on Twitter and Google+!