A couple of years ago I attended the PhD defense of a fellow student. That was in the overly stern math department of a fairly stern university. Therefore, any venture into making jokes had to be carefully pondered.
Although his defense talk was beamed as attendees were entering the room, the pdf-viewer window wasn't maximized so that one could openly see other elements from his desktop.
I thought to myself: "Weird, why would he go through the trouble of plugging his computer and beaming his screen but not having his talk fill the screen?".
As I and many others had arrived early to get a good spot, I started exploring his screen that he had skillfully filled with many small Easter eggs, key among which was the pdf file name that you could read in the window title bar. It read something like:
When time came for him to get started, he just maximized the window and gave his talk. I hardly remember any other talk I attended but this one struck me.
Another one I did myself when giving a seminar talk was the introduction a blue slide in the middle of my talk. I just knew that my talk would be boring as hell to those uninitiated attendees (>99%) and hated it when, as a speaker, you see the audience's attention drifting away. So I carefully reproduced this blue image shown when the beamer has no input signal. When I hit the slide, I could see everyone happy at the idea that the talk would be shortened. Yet the next slide said (still on a blue background):
This is the beamer speaking:
Your talk is easily the most boring one I've ever beamed, please wrap it up soon.
Of course everyone laughed and bore with me until the end.