Kind of an out of left field question: Lamport appears in a little square of video occasionally overlaid on the slides and sometimes full screen. As far as I can tell, he never recycles an outfit and seems to switch head gear regularly. The switch is often between segments that are quite short.

It feels almost like an intentional joke. Do you think that is the case? Or just even short segments were recorded on different days and Lamport like to wear all sorts of hats? That one where he's wearing a beanie and indoor sunglasses seems particularly intentional.

I've never met him, and the delivery of the lecture seems fairly dry and serious, so I can't tell :)