 The only character developed with a racial description in mind was Dr. Miranda Bailey , who is portrayed by Chandra Wilson . The character was written as a tiny blonde with curly hair , but when Wilson began speaking , Rhimes reported : " [ Wilson ] is exactly who Miranda is . " James Pickens Jr. was selected to appear as Dr. Richard Webber in the series ' pilot and first season . Katherine Heigl wanted to portray Dr. Izzie Stevens as a brunette , but was requested to retain her natural blonde for the part . Isaiah Washington , who portrayed Dr. Preston Burke , initially read for the role of Shepherd , but was cast as Burke , because the original actor to play Burke had to withdraw . T. R. Knight signed on for the pilot as Dr. George O 'Malley , expecting that the role might be short @-@ lived , because he liked that the character was multi @-@ faceted . Rounding out the season one cast was Justin Chambers as Dr. Alex Karev . 
