Wildest situation I ever saw. An IM attending decided to go back and do a residency in EM. I was a med student and he and I were working up a patient in the ED. We go to present the case and the EM attending is a guy who is in his first year out and had been an intern and a resident on this now EM intern's service. The "intern" presents the case and the attending pauses and says "You realize how weird this is right?" They both had a good laugh about it. It helped that these were two of the best guys I've ever met in medicine. First names all around.