(USA) Directed by Jon Hurwitz, Hayden Schlossberg. Starring Jason Biggs, Alyson Hannigan, Chris Klein, Seann William Scott, Eugene Levy. Category IIA.

Why do people choose to go to their 13th high school reunion? Where would Stifler defecate to get back at a group of teenage punks? What does a butt-naked Jason Biggs look like? These are just a few questions that should never be asked in the first place, and yet are answered in “American Reunion.”

Despite being a teen sex comedy monument of generation-defining importance, “American Pie” has no reason to be baked repeatedly after its initial success in 1999. Sadly, two inferior theatrical sequels and four abysmal straight-to-DVD spinoffs later, the tired series drags on with yet another installment. Helmed by Jon Hurwitz and Hayden Schlossberg, the writing-directing duo behind the “Harold & Kumar” films, “Reunion”—like its predecessors—is relentlessly driven by gross-out antics and genital jokes. For a generation of moviegoers that have outgrown such humor, all the shenanigans and sexcapades carried out here by an array of grown-ups are no longer cute, but cringe-inducing.

Thirteen years after their high school graduation, members of the Class of ’99 reunite in their hometown of Michigan—each with their own life crises. Jim and former band camp nympho Michelle (Alyson Hannigan)—who are married with a toddler son and a non-existent sex life—arrive and stay with Jim’s now-widowed father (Eugene Levy), hoping to rekindle their bedroom fire during this vacation. Oz (Chris Klein) has become a famous TV sports anchor with a wild model girlfriend (“30 Rock’s” Katrina Bowden) and appeared on a celebrity dance show that people now like to make fun of. Contemplating fame and love, he runs into high school sweetheart Heather (Mena Suvari), whose doctor boyfriend is a total douchebag. Happily-married architect Kevin (Thomas Ian Nicholas) comes solo, and things get complicated when he realizes he still has feelings for old flame Vicky (Tara Reid). Finch (Eddie Kaye Thomas) tells people all about his globe-trotting adventures, and sparks fly between him and ugly-duckling-turned-swan Selena (Diana Ramirez).

Then, there’s Stifler (Seann William Scott)—the prankster, the man-child, the Stifmeister. Escaping from his dull temp job, he really gets the party started with his unchanged foul demeanor and 12-year-old mentality. If there are moments in the movie that make you chuckle a little, it’s probably him pulling one of his vulgar stunts. And don’t forget the teen hotties and Milfs. Kara, Jim’s young neighbor who he used to babysit, wants to lose her virginity; and the legendary Stifler’s Mom (Jennifer Coolidge, immortalized by her role) is surprisingly not the only cougar in the picture.

For most part, “Reunion” is a strained and predictable bore. The uninspired material is recycled from previous installments; and now that the world has seen “The Hangover,” the “Pie” gags seem outdated and tame. However, the writers and directors do make a wise decision by playing the “nostalgia” card, as that’s pretty much the only reason anyone would want to see the flick. With 90s’ pop rock/R&B hits (“This is How We Do It” and “Closing Time” are on the playlist) playing everywhere in the background, the characters reminisce about the good ol’ times vaguely and forcedly, and then try to relive the past. The problem? At 17, those teenage horndogs’ immaturity and sex-obsession made them obnoxious but also endearing and resonant; in their 30s, it’s just downright obnoxious. If there’s any redeeming factor, the adorable Levy is scene-stealing as always, and shows genuine emotions in a few dramatic sequences.

Though advertised as the last piece of the “Pie,” the ending of “Reunion” still hints for potential sequels as Kevin says to the gang that the reunion was fun and they should do it every year from now on. I don’t know what he’s on to make him think that, but somebody please shut the “Pie” hole before “American Retirement” gets made.