Tonight's the night that thousands of fans of ER have been waiting for, the return of Jennifer Aniston! Oh wait, that's 30 Rock that she'll be on tonight. Never mind.

Actually, tonight is the night that Dr. Mark Greene (Anthony Edwards) returns to County to try to save the life of Dr. Banfield's sick son. As we told you last week, Greene isn't really alive and he's not a ghost. It seems that Dr. Banfield came to County with her son and husband, years before she became the new head of the ER, and Greene was the doctor who worked on her son. Her memory (and the flashbacks) are triggered by a current story where Banfield is trying to save the life of another child who comes to County.

Edwards isn't the only one who comes back. Since most of the episode takes place years ago, we also see Laura Innes as Dr. Weaver and Paul McCrane as Dr. Romano. Innes has a rather dramatic entrance in the clip after the jump!