In any film with a mystery at its center, the denouement is bound to be unsatisfying, as rational explanations for bizarre circumstances are never more interesting than the circumstances themselves. This is true of Vegas buddy comedy “The Hangover,” but only to a point. After having explained away most of their strange post-blackout circumstances through means both reasonable (macho displays of extreme dentistry) and less so (Mike Tyson, of course ), the foursome return to hearth and home, only to discover a camera on with which they’ve documented their unremembered exploits, which play out in a slideshow as the credits roll. Like the rest of the film, the snapshots are hilarious because they’re positioned just slightly beyond the believability barrier as an epically debauched Vegas trip (had some of these images lingered onscreen for half a second more, it’s possible the MPAA would have bumped the R-rated film into the next ratings bracket), but most importantly, they introduce a host of new mysteries that are left delightfully unresolved. Why the hell would Ed Helms want to punch out Wayne Newton? Exactly.