At one point in this revue, skinny Will Clinger and Jim FitzGerald make fun of their physiques by posing as "The Buttless Boys," a pair of British buskers who dance a strutting dance without using their buttock muscles. But in every other respect, these fellows have plenty of cheek, and they exhibit it shamelessly. Clinger is the tall gangly one who looks like a cross between Dick Van Dyke and Bruce Dern; FitzGerald is the dimpled, diminutive pup who recalls 60s folk-music comic Hamilton Camp. In this latest incarnation of a cabaret act they've been working on since 1988, they offer an engagingly odd mixture of improv-style sketch humor, self-deflating stand-up, and original musical routines that suggest turn-of-the-century British music hall and small-town American vaudeville as filtered through the warped minds of guys who grew up listening to classic rock on one hand and the records of Tom Lehrer, Stan Freberg, and Flanders and Swann on the other. Their current material includes several bad-taste medleys (The Wizard of Oz as rewritten by Bernhard Goetz, a collection of smarmy male-chauvinist pop standards, an anthology of rock anthems as interpreted by a Las Vegas lounge act); a deliciously snotty parody of boozy Irish raconteurs Frank and Malachy McCourt's long-running show A Couple of Blaguards; an Oscar winner's vindictive speech in which he dedicates his victory to all the people who stood in his way; a bit of bittersweet small-town nostalgia from the pen of Randy Newman; a Broadway musical version of Psycho; a little of the old soft shoe; and even a few sea chanteys. Throughout this and plenty more, they veil some extremely tight teamwork behind an off-the-cuff demeanor and rarely shrink from any excuse to toy with the audience. David Whitehouse provides the first-rate piano accompaniment, along with a synthesized rim shot or two. Ba-dum-bum. Halsted Theatre Centre, through August 4. Thursdays and Fridays, 8:15 PM; Saturdays, 6:30 and 9 PM; Sundays, 7 PM. $14.50-$18.50.