“Harold and Kumar Escape from Guantanamo Bay” is an act of pure genius — not because it’s a great film, but because if it does well at the box office, its makers will be hailed as political satirists of the highest order who have provided a much-needed laugh break in the midst of the soul-deadening war on terror. And if it flops, they’ll be box-office martyrs, misunderstood and underappreciated by nervous Americans with a case of the “too soon!” jitters. Either way, they’ll get far more respect than they deserve for this timid yuck-fest.

While it barely made a whimper at the box office, 2004’s stoner love song “Harold and Kumar Go to White Castle” became a DVD hit, an “Up in Smoke” for the boomers’ babies. The sequel, which opens today, picks up the tale of Harold Lee (John Cho) and Kumar Patel (Kal Penn) the morning after they return from White Castle. The girl of Harold’s dreams has taken off for Amsterdam and, lured partially by the siren call of smoker cafés, the duo decides to go after her to pitch woo and get stoned. On the plane, Kumar fires up his smokeless bong (patent pending), causing the hapless duo to be mistaken for terrorists, and they’re thrown into Guantanamo Bay. Five minutes later, they escape.

Up until this point, the film, co-written and directed by Jon Hurwitz and Hayden Schlossberg, has gotten all its mileage out of the title, which turns out to be the funniest thing in the film. But once we get to Gitmo, it becomes immediately apparent that the creators are going to chicken out before fulfilling the titular potential. The infamous prison is depicted like any anonymous Hollywood hillbilly lockup, full of big-bellied guards ready to violate the boys on a bale of hay. After Harold and Kumar escape, the film fires off its last political joke when they casually hitch a trouble-free ride to America with a boatload of chilled-out illegal immigrants.

Their subsequent trip to a “bottomless” party, an overnight stay with a gang of surprisingly couth rednecks, and their invasion of Kumar’s ex-girlfriend’s wedding to an L.L. Bean bully has occasional pop but, for the most part, it’s reheated comedy leftovers. We’ve seen the nasty Southern prison seething with the threat of rape before. Most of the jokes are about racism, not the war on terror, and they were all done better and fresher by Mel Brooks, Richard Pryor, and Eddie Murphy decades ago. The nadir arrives when our heroes haul out Neil Patrick Harris for yet another cameo as himself. Watching Mr. Harris ride a unicorn over a rainbow is undeniably ironic and entertaining, but while the gag was fresh and out-of-left-field in “White Castle,” here it’s just Paul McCartney on tour singing “Yellow Submarine” one more time.

Harold and Kumar certainly aren’t the problem. Although they’re painted with broader strokes this time around, Messrs. Cho and Penn have more chemistry than a bioweapons lab. Mr. Cho plays such a perfectly conflicted striver that you can practically hear his grandmother in the background nagging him to get married, while Mr. Penn manages to make mouth-breathing math nerds seem like aspirational icons. But the filmmakers were apparently so exhausted by coming up with such a perfect title that they returned their intestinal fortitude to the store immediately thereafter, leaving us with a movie that wants to be brash and funny but is too toothless and timid.

Almost every scene is either a lost opportunity or a joke so old it could’ve been in vaudeville. Dropping a dark-skinned joker into a Klan rally was funny when Pryor did it a quarter-century ago in “Bustin’ Loose,” less funny eight years ago in “O Brother, Where Art Thou?,” and incapable of raising a single stoned giggle here.

The most disappointing thing about “Harold and Kumar Escape From Guantanamo Bay” is that the entire film is a lost opportunity to milk some much-needed levity out of the humorless and interminable war on terror. To slightly rephrase President Bush, “Everywhere that laughter stirs, let tyrants fear.” In theaters, where “Harold and Kumar” is playing, the laughter is barely a rustle, let alone a stir.