I have a similar anecdote which completely stunned us, but which may possibly be part of his standard routine, and thus something he does for every set of students:

He always wore the same striped sweater. At one point, he took a break to drink some water and remove his sweater. But beneath the sweater was another identical sweater!

I assume everything he did was very well-planned and part of his pedagogic system and routine, but it was often hard to tell if he was acting, or if he was actually being serious but eccentric.