Disrespectful/joking behavior behind the scenes is not too rare with doctors, either. I have doctor friends who attest to this, as in, they engage in this behavior (so again, no game of telephone here). Never in front of the patient, since that would be rude and unacceptable, but privately with other physicians? You bet.
You are justified in being skeptical, but unfortunately you're not going to find the evidence you seek on HN. By definition, the written word here is not going to be proof enough. If the topic interests you enough, I guess you'll have to speak to doctors and students directly?
EDIT: I realize I should clarify based on some of the sibling comments... nobody was doing anything obscene with body parts. I'm referring to commentary, jokes, dark humor.
Yes, same with my anecdotes. I was talking about dark humor, not doing anything obscene with body parts. I think nobody else mentioned anything obscene, either.