Playing parts better suited to the periphery of Mean Girls, a trio of dynamic actors do what they can with playwright - director Leslye Headland's thin, unvariegated material: Regan (Kirsten Dunst) is the seething maid of honor; Katie (Wedding Crashers» gifted Isla Fisher) is
a bobbleheaded sex fiend; and Gena (Lizzy Caplan, most alive when her cell is tossed out a window) is the caustic slacker, still bruised over a high - school rejection.