An improvisational musical is like the proverbial walking dog: The miracle isn’t that it’s done well, but that it’s done at all. With iMusical, Washington Improv Theater trots out a dog that hops, skips, and can-cans for an hour and change of consistently gleeful, new-under-the-sun musical comedy. Here’s how it works: Upon entering the theater, every audience member scribbles an imagined location on a strip of paper. (This is the extent of iMusical’s Whose Line Is It Anyway–isms.) One of the actors chooses a strip at random, and the show begins. That melody, plot, and dance prove as winsome as their counterparts at the KenCen (and for, ahem, a fraction of the price) is second to the joy of seeing a fully imagined show produced from scrap—er, scratch.

IMUSICAL’S FINAL PERFORMANCE IS AT 2 P.M. AT SOURCE, 1835 14th ST. NW. $15. (202) 204-7760.