Grey's Anatomy

The character Alex Karev was not in the original pilot script; his role was inserted into the pilot as an afterthought in order to provide a foil, as well as male companionship for Dr. George O'Malley. Since he wasn't added until after the pilot was shot, scenes with him were either re-shoots or digitally altered.

As is common for major TV and film productions, stars of the show have become famous in roles other than those they originally sought. Sandra Oh was initially looking to audition for the part of Dr. Bailey. On The Oprah Winfrey Show (1986), Isaiah Washington (Dr. Burke) said that he had auditioned to play the role of Dr. Shepherd.

Shonda Rhimes said on an interview that she had a clear idea thought for the show's end, but its success kept growing to the point of her ending no longer being proper, so she decided to use the idea on a storyline and come up with another ending.