Strange things can happen when you set a small, intimately scaled play on a big stage. Putting David Mamet’s 1975 American Buffalo—a taut suspense piece about three guys plotting to steal a rare coin—on the Rep’s mainstage rather than in the smaller Leo K. Theatre yields an Alice in Wonderland effect.Eugene Lee’s towering set turns Donny’s resale shop into a multilevel warehouse of categories of stuff (e.g., a chain gang of floor lamps). It’s more like a confiscation depot than the dumpy junk shop traditionally depicted. Against these epic surroundings, director Wilson Milam and his actors make unconventional character choices. Charles Leggett, sporting a ducktail as Donny, flattens his speech, measuring it out punctiliously in a way that estranges him from us and from his old buddy Teach—Hans Altwies, who rules the stage every moment he’s on it. He’s wonderfully entertaining, though his bizarre, laser-precise Saturday Night Fever moves and hair-trigger reactions render him a showman/clown. But by far the weirdest choice is to have Zachary Simonson play Donny’s assistant Bobby with Asperger’s. The literal-minded youngster of the trio, Bobby is the script’s mechanism for sympathy, a well-meaning waif. Trussed by Deb Trout in a leather jacket so small as to resemble a bolero, Simonson’s body seems shriveled into an S shape, as though permanently absorbing a blow. His words emerge in a monotone so irritating that one dreads his appearances, which was surely not Mamet’s intent; worse, it undercuts the power of the ending.Staged in this existentially cavernous wasteland, this is not typically juicy Mamet. When you’re mounting a show as widely seen and enjoyed as this one, it’s challenging to keep it surprising. This production certainly does that. stage@seattleweekly.com