You can tell a lot about a person by how they respond to a hangover that blanks out the memory. Do they contemplate those missing frames with humor or dread? I once woke up from a fantastic party with a headache so vicious it felt like pain was physically spilling out of my ears and onto the bed sheets. I was happy enough with the night before until I realized that the pistol I had received as a graduation present was nowhere to be found. Whoops.

My problem turned out fine, but others have it much worse. “This just means we had a great time,” says Phil (Bradley Cooper) the night after his buddy’s wild Las Vegas bachelor party. He hangs onto this belief even after discovering a tiger in the bathroom, a missing infant in the closet and the keys to a stolen police car among other things. I can’t help but admire his optimism to a point: what’s done is done, so enjoy the spectacle.

His pal Stu (Ed Helms) sees the downside of things, such a felony arrests, missing teeth and the fact that the hotel has his credit card on file. The best man’s future brother-in-law, Alan (Zach Galifianakis), is such a scatterbrained imbecile that it’s difficult to tell whether or not he even knows where he is. All three of these men do have one common concern: where did the groom go?

Todd Phillips’ “The Hangover” is at its core an unapologetic celebration of male bonding via lewd, booze-and-drug-fueled partying. I confess that I’ve always pitied my friends that permanently abstain from throwing caution to the wind and embracing the playfully indecent, as nothing short of serving in a war adds so much to the friendship of quarter-aged men. The endearing effect of mischief is on full and accurate display here, aided by surprisingly layered performances from the three leads and a script that gets the important parts right.

The film’s straightforward vulgarity and wit means that its staggering box office success ($200 million and counting) is a relief during a period where screen comedies are becoming increasingly defined by Will Ferrell-style post-modern mugging and Judd Apatow-style “sweetness.” Phillips demonstrates no interest in either, doing what Mel Brooks might call “rising below vulgarity” with a simple enthusiasm for the material and respect for the actors scoring the laughs.

It’s to the filmmaker’s credit that even though the laughs begin to thin out in the final stretch, I hardly noticed, because by then the characters and plot had possessed my attention well beyond what I thought possible going in. There are even flashes of brilliance, such as Stu’s pathetic defense of his indefensible girlfriend. He delivers a line thats humor masks its commentary on our culture’s perception of sexuality and certain hypocrisies.

Zach Galifianakis has received the most attention for his performance as a man who sincerely wishes the best but whose ineptitude nearly leads to ruin for the group until a harebrained scheme yields unexpected dividends. Bradley Cooper, now plastered on every other page of Entertainment Weekly, proves that not only is he an expert at playing the best friend, but that he’s even better when the movie is actually about that best friend.

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