When JD fantasizes the OB/GYN girls as a sorority, their letters are Omega Beta Gamma (OBG).
The actress who plays Jordan (Christa Miller) is actually pregnant with her second child with Scrubs creator Bill Lawrence.
In online syndication, every one of the songs has been changed, likely due to royalty restrictions.
Even though they do a good job "blocking out" all the license plates in the series, if you look closely, they say "Drive Safely" where the name of the state usually is found, though it's in the style of the California state license plates. This is one of the ways they keep the anonymity of what state the show is suppose to be set in.
When Carla goes off on JD for interrupting her phone call and starts listing off issues she's dealing with, she mentions still having to go home to put out canned food for her cat. This is the first and last time the cat is mentioned.