i.e. precisely 50 words, no more or less.
The concept is a bit hackneyed, but that doesn't matter. Apparently they're called Minisagas, who knew?
Anyway, I've not written any (well, not yet - my thing at the moment is writing a long story with as few different words as possible, but that's a whole other story (see what I did there?)) but it struck me the other day that the middle spoken section from "They'll Need A Crane" by They Might Be Giants might intentionally be one.