If you’ve ever spent a Saturday evening home alone watching a “Whose Line Is It, Anyway?” marathon on ABC’s Family Channel (not..that…this DCist…has), you probably know that when it comes to improv theatre, it’s hard to predict what’s going to happen. Actors never know what kind of suggestions they’ll get from the audience, and how well their team will respond under pressure. This can make for exciting, if uneven, entertainment, and Washington Improv Theater…