You mean follow him around pretending to talk into your cuff or cup an earpiece... or perhaps just say hi with "violence in [your] eyes"?
That is one of those things that I don't want to laugh at but I really can't help it. I mean on one hand the guy is clearly mentally ill and it probably isn't a good idea to agitate him any further but on the other hand man it would also be funny to watch him wig out irrationally over a simple prank. I am conflicted