A pretty good ‘Hangover’

If there is any justice in the universe, “The Hangover” will make Zach Galifianakis a household name.

As the odd man out in a quartet of bachelor partiers, Galifianakis’ bearded weirdo Alan blithely stands around in a jockstrap and athletic cup – then goes in for a hug from his future brother-in-law.

He laments being banned from pleasuring himself on an airplane, which he blames not on common decency but on Osama bin Laden.

And he wears a man-purse better than anyone in Hollywood.

It’s Galifianakis’ all-out performance that makes “The Hangover” the funniest comedy since Judd Apatow’s “The 40-Year-Old Virgin.”

Our story begins on the wedding day of Doug (Justin Bartha) and Tracy (Sasha Barrese). The phone rings, and the bride hears the voice of best man Phil (Bradley Cooper), whose first words to her are, “We (blanked) up.”

Flashback two days earlier, when Doug and Phil are joined by Alan and Stu (Ed Helms of “The Office”) on a road trip to Las Vegas. Upon checking in to Caesar’s Palace, the four make a Jagermeister toast to what surely will be the best bachelor party ever.

Flash forward many, many hours later. Three of the four have passed out in a heroically trashed hotel suite, clueless about what has transpired. And they have only a few hours to find the absent groom.

Unlike so many Vegas movies before it, “The Hangover” avoids glamorizing alcohol-fueled, consequence-free debauchery. Instead, it focuses on the aftermath of buffoonery and the mystery of the epic night out. It’s “Swingers” meets “Memento.”

Director Todd Phillips also helmed “Old School,” another quotable testosterone-soaked, college-guy movie that eventually found its way into heavily censored rotation on basic cable.

Like “Old School,” “Hangover” assembles a solid cast – from Helms’ henpecked dentist Stu and the excellent Rachael Harris as his cheating girlfriend to Rob Riggle as an overzealous Vegas cop and Ken Jeong (the angry OB/GYN from “Knocked Up”) as an effeminate and angry hostage.

But ultimately, it’s Galifianakis who sells it, much as Ferrell stole “Old School.” Their shticks are similar: Both play characters who will stare blankly at anyone who does not share their absolute conviction, and neither is ashamed to run around without pants.

In case it’s not clear: “The Hangover” is vulgar, raunchy, filthy – pick a grandmotherly adjective. This is a movie that manages to make funny out of 9/11, the Holocaust, date rape, child abandonment and, yes, a masturbating baby.

While it certainly lacks the treacly heart of the compulsively sweet Apatow films, it’s all the better for it.