I noticed in the episode "Academia Nuts" (season 2, episode 7) that Dr. Canfield introduced Doogie as an attending physician to Mrs. Bea Portmeyer. Though, from what I remember he was still a resident in season 2 and didn't become an attending level (via a fellowship) till the end of season 3.
I say he became an attending level, because fellows are at the attending level, but don't yet have the title of attending in the area they are specializing. Fellowships are between Residents and full attending in a specialty. You can actually be an attending (say in Family Medicine / GP) and a fellow in a specialty (e.g. trauma surgery or internal medicine).
So, I guess I'm asking when did Doogie become an attending in any area?