For whatever reason, Sean doesn’t think to ask the Mob to compete with him in Vegas (surprise: they turn up anyway), instead relying on Moose to recruit a new crew composed of dancers featured in the past three movies. Moose’s first stop: “Step Up 2 the Streets” star Briana Evigan, back as Andie, who needs no excuse to quit her fashion-industry gig — or to drop everything mid-shoot and battle Sean in a room full of giant yellow balloons.