Globophobia
The presentation had gone pretty well, I thought; yes, I was riffing off the slide deck rather than working from memory, but that’s a longer-term goal.
My organising metaphor was the balloon arch, and I’d prepared enough in advance that I had ordered a pack of balloons of different sizes to hand out so that people had something to connect with and remember after the event.
It worked better than I’d thought — people up the back even assembled their balloons into an actual arch, even without the full set of equipment to do so.
The room was engaged, the Q&A was good; but then I was checking in about what would happen to the balloons afterward, and people were quietly, efficiently looking to dispose of all the balloons.
It was then that I found out that someone in the room had severe globophobia - a fear of balloons. No one had known, except the person, but I learned a further lesson around checking in with an audience ahead of time to try and accommodate everyone as much as possible, so that a talk can work for everyone.