There was an episode where Turk surprised Carla with a bus pass so she can go to nurse practioner school (for a Master's degree in nursing). Then in a future episode, Carla and JD had a fight about how he thinks he is better than her because he's a doctor. He mentioned something about college, and she said she never went to college. The slip-up is, in order to get a master's degree in nursing (become a nurse practioner), you have to have a bachelor's degree in nursing (RN BSN), ie, go to college.

Nurses can get an LPN lisence, or RN lisense by attending nursing school, but to get their master's degree in nursing they would need to earn the necessary credits for a bachelor's first.

Pretty important considering it's a show about a hospital with doctors and nurses. It's still a great show, just thought I'd give nurses their credit where it's due!