Reuniting after almost a year spent pursuing separate projects, Will Clinger and Jim FitzGerald are pairing up again for a new revue, The Tall and the Short of It, opening later this month at the Milwaukee Repertory Theater; to get in shape they've booked two evenings at the Improv Institute, whose almost-anything-goes ambience should suit the team to a tee. Clinger--he's the tall of it--is the gangly guy who's been cohosting channel 11's Wild Chicago since last summer; his diminutive partner FitzGerald recently finished playing the fool--literally--in Shakespeare Repertory's King Lear. Together they're a charming and cheeky duo who hide a tightly focused ensemble awareness behind a disarmingly casual stage presence. If their new show is anything like Whose Act Is It Anyway?, which they performed around town a couple of years back, it will be an engaging, unusual mixture of improv-style sketch comedy, drolly self-mocking stand-up, and neo-vaudevillian musical routines. Pianist David Whitehouse is an integral and able part of the show, as are special guests Elliot Cutler (he juggles toilet plungers) and monologuist Kate McClanaghan. Improv Institute, 2319 W. Belmont, 929-2323. Wednesday, April 7 and 14, 8 PM. $5.