"It's not so hard to see why Zebro, the Boston-based comedy troupe of recent and soon-to-be college grads, packs a standing room-only show at the ImprovBoston every Tuesday. Their freewheeling shows are spit-valve releases of "Mr. Show"-esque detritus, a near-ramshackle combination of skits, stand-up and video that's rare for a city that favors the more traditional comedy club circuit"