Ah, were you thinking of something more large scale? I guess it would just be a case of trying to spread a prompt and invite/encourage responses via journal, with the interest of seeing what different people come up with. Perhaps people could drop a link to their own responses into any comment they make on others, and thereby alert readers who follow the OP that they are participating? A bit of cross-journal traffic might come of it.

Whether LJ posting is even already too quiet to try this sort of thing, I don't know :o( I only have a handful of people on my list who actively post fic on their journals, and two of them are you and I, for example! Drabbles are quick, though...