Corrected entry: Keith, Lisa, Rex and a few others were JDs interns at the start of season five. Then once Keith starts to date Elliot, they suddenly become Elliot's interns. The interns Elliot had earlier in the season just disappear.
Corrected entry: The janitor's lines are often unplanned, with the script simply saying, "Janitor says something".
Correction: Incorrect. The Janitor has lines, but often does variations of them. As evident by the fact that his co-stars always manage to have suitable responses.
Corrected entry: At one point, it is revealed that the Janitor's name in the show is Neil Flynn (the actor's name), and J.D. sees him in a bit part he played in the Harrison Ford movie "The Fugitive." So, in essence, while everyone else are fictional characters, Neil Flynn is playing himself - as a sadistic janitor.
Correction: The Janitor's name is never actually revealed; Neil Flynn's real-life past was used to give his character some depth, but the latter remains known to all and sundry only as 'Janitor'.
Corrected entry: The shot of J.D. walking toward Sacred Heart hospital is re-used so many times. Note the lady pushing the man in the wheelchair and the two doctors standing by the wall talking.
Correction: How is this a mistake? It's just a recurring shot used over various episodes.
Correction: The interns just switched attendings. Whilst Turk's been at Sacred Heart he's had numerous attendings.