Dr. Reid's clothes are same as on the previous episode while she was singing "I told you so" song in one of the intern's fantasies.
Until this episode (163rd), it's 1st time where J.D. doesn't play (there was one where he talks by phone).
Also it's the 3rd for Dr. Cox and Carla, and the 4th for Dr. Kelso and the Janitor.
And Turk hasn't been in 3 and Elliot in 2.