A few years ago, I read an article in which it was revealed that while the movie Flash Gordon (1980) was being filmed, the legendary ham, Brian Blessed, kept making laser noises (i.e., saying "Pew Pew!") every time his character fired a weapon. Because the director didn't want people to see the character's enormous mouth1 moving with each blast, the battle scenes had to be refilmed.
I think this is one of the funniest things I've ever heard, and I have been trying to find the article again for over a year now, with no success.