People may remember that I am a fan of the author Christopher Priest. (The Prestige is a particular favourite, and much better than the film adaptation of a couple of years ago.)
Many years ago, he told the story of how at one SF con, Larry Niven was being a very boring 'guest of honour' so Brian Aldiss (someone else who's career has suffered by being pigeon-holed as 'just' a SF writer) pretended to have a nosebleed in order to escape. A few years later, Christopher is guest of honour and sees that the front three rows all have handkerchiefs at the ready!
Anyway, I've never needed to have a 'Niven nosebleed'.. until last night. I was very pleased to see that they do work, especially when the alternative is interrupting something that doesn't want to be told it's a complete load of crap.