What happens in Vegas, stays in Vegas … to the point of complete memory annihilation, as in the case of “The Hangover,” where four friends set out on a bachelor party trip that goes very, very wrong. The laugh-out-loud-funny movie tells their travails in piecing together the night's mysterious happenings on the morning after. Why is there a tiger in the bathroom? And a baby in the closet? And where's the car, and … the groom, who's supposed to be married today? Over-the-top and outrageous, it's the best Vegas trip we've taken in a while.