I never liked this show... But I fucking laugh my ass off everytime they
break character to do shit like this... I guess my music bug twitches
everytime...
+João Ribeiro Except that they aren't breaking. The whole point of the episode is that one of their own surgeons is in the hospital, and she's having hallucinations, causing it to look like the cast is singing. They worked in this theme beautifully, actually.
Most cases it's not characteristic of the characters to leave. Think of the case of Derek. He had a family and a job and everything. There's no way to incorporate a storyline where he leaves. Derek and Meredith have been through way to much.