Severn Darden is in a very brief uncredited scene (just over one minute). Using his German professor character from his famous "Metaphysics Lecture", he plays a psychiatrist analyzing Mickey. This gives us a clear glimpse of his performance in that routine.
Guest star Hans Conried legendarily lost his temper during the shoot, not liking the "Monkeeshines" of the group, and declared "I hate these f***ing kids!" The cameras stopped and a break was called, to let Conried calm down. Micky Dolenz admired Conried, and later regretted the incident.