Katherine Heigl
There's a reason why Katherine Heigl always gets typecast. She only fits the role as the vague blonde love interest with a boring career because she's notoriously difficult to work with. After her time on Grey's Anatomy, she was furious with how her character was written and caused tons of drama on set. She appeared in films like Knocked Up, 27 Dresses, and Life As We Know It, but all of those roles are pretty much exactly the same.
That Wild Plotline
In Heigl's defense, her character did have one of the most unbelievable storylines in an attempt to write her out of the show. Dr. Izzie Stevens fell in love with a ghost, then got cancer, then just up and left Seattle Grace Hospital. Shonda Rimes had probably had it up to here with Heigl's drama and didn't want to give her a graceful exit from the show.