Tip #2 The fewer characters the better. Don’t use more than two of them.
From upcoming book: 52 TIPS FOR WRITING Flash Fiction, Sudden Fiction, Drabbles & Other Short Fiction
Writing flash fiction is difficult enough and please don’t clutter it with too many characters. Two characters are optimal. One is even better. Some novels need a major cast of characters, but not your flash fiction story. As a flash fiction writer you only have a few sentences to tell the story, don’t clutter it up with a horde of characters. I think I only broke this rule once by using three characters, but even for me, it doesn’t happen very often. Keep the number of characters to a minimum.