Stop me if you’ve heard this one.

A bunch of friends decide Vegas would be the ideal destination for a bachelor party. They get wasted. They wake up. They don’t remember anything.

Sound a trifle clichéd? Perhaps a wee bit tired?

Okay…how about we sprinkle in a Mike Tyson cameo, a chicken wandering around a $4,200/night suite at Caesar’s Palace, a doped-up tiger, a piano interlude by Ed Helms, and an effeminate, naked Chinese gangster with a tire iron?

See? Now you’re interested. And you should be.

The Hangover, from Old School director Todd Phillips, could have been a disaster of epic proportions. But it’s actually one of the smartest comedies (if not the smartest) to come down the pike since Tropic Thunder.

The Hangover works because it’s driven (very effectively) by the pitch-perfect characters, not by the events at a raucous bachelor party. In fact, we never see any hint of what happened at the party until the closing credits.

Helms, Bradley Cooper, and Zach Galifianakis play 3 friends who lose the groom somewhere during the previous night’s events…and spend a hilarious next day and night looking for him. Each gent has his own traits and quirks, but none of them are cartoonish. And the movie is infinitely more watchable as a result.

The structure also helps. The Hangover starts with us finding out only that something went drastically wrong, and then it jumps to ‘Two Days Earlier’ mode, so we can begin putting the pieces together.

The ride is one of the most entertaining that you will take in a theater this summer. The laughs are constant, the situations are flat-out hilarious, and the cast (from the main guys to the wedding chapel owner to the long-overdue-for-a-comeback Heather Graham) is top-notch.

The Hangover feels like a well-thought out story, instead of just a bunch of crazy situations patchworked together into a movie. A lot of thought went into this, and it shows. Don’t get me wrong, the humor is raunchy and waaaay off-color, but it’s the difference between, say, Old School and the infantile National Lampoon’s Van Wilder.

And plans are already underway for a sequel, which will hopefully allow the Phillips to explain how that crazy chicken ended up in the suite.

4/5 stars