The American Stage production of The Mystery of Irma Vep is such good-natured, silly fun for most of its length, you can almost forget that its last quarter or so is redundant and a trifle tedious. Still, this is a case of too much of a good thing: Matthew McGee and Brian Webb Russell are so hilarious as they romp through Charles Ludlam’s farce, we don’t need a full two hours to feel happy and fulfilled.

The quick changes that have the two actors playing multiple parts, the unexpected appearance of horror figures from an H. P. Lovecraft story, the offhand references to Shakespeare, Ibsen and Hitchcock — all combine to make Irma Vep a winning experience for a good 90 minutes — and then we reach saturation. Cut the last half hour, and this frolic would be just about perfect.