The collective luck of Jim, Michelle, Stifler, Finch, Kevin, and the filmmakers has finally run out with "American Wedding," the third installment of 1999's "American Pie" and 2001's "American Pie 2." Whereas its predecessors effortlessly blended outrageous and raunchy comedy with an undeniable truth and sweetness, the humor in "American Wedding" is more often uneven than not and its serious moments less convincing and real. Written by Adam Herz as if he was more won over by his salary than a genuine passion for the story he was telling, the film is ultimately burdened by this very notion—a distinct feeling of nothing more than obligation for all involved.

Why the movie wasn't simply called "American Pie 3" is anyone's guess, even if the new title says it all. Upon graduation from college, nice guy Jim (Jason Biggs) digs up the courage to propose to long-time, former band camper girlfriend Michelle (Alyson Hannigan). When she accepts, the extended wedding plans begin, with Jim seeking the aid of best friends Finch (Eddie Kaye Thomas) and Kevin (Thomas Ian Nicholas) to ensure that everything goes off without a hitch. It doesn't, of course, especially when self-involved horn-dog Stifler (Seann William Scott) catches wind of the marriage plans and attempts to romance Michelle's beautiful younger sister, Cadence (January Jones).

If the high school-set "American Pie" set up characters we grew to love, and the college-themed "American Pie 2" continued their natural progression with a surefire accuracy, then "American Wedding" never feels like anything more than tacked-on. Post-college marriage is certainly the next step in these characters' lives, but the writing this time isn't nearly as sharp or witty, and most of its characters have ridiculously little to do. In fact, past cast regulars Chris Klein, Tara Reid, Mena Suvari, Shannon Elizabeth, and Natasha Lyonne are not only nowhere to be found, but aside from one passing exception, are never even mentioned. This is not only a disappointment to the series fans who have invested into all of the characters, but it is lazy on screenwriter Herz's part. Their absence is strongly felt.

"American Wedding" does try to follow the formula that worked for its precursors, but by now, that formula is getting notably stale. For the most part, the jokes arrive out of necessity rather than through naturalism, even if several set-pieces are quite funny. Jim and Stifler's run-in with a wedding cake and two dogs is a comic highlight, the culmination of its setup ribticklingly ballsy, while a bachelor party gone awry reminds of a superbly edited screwball comedy. Less successful is Stifler's dance-off in a gay bar and Jim's untimely decision to shave his pubic hair.

The center of the film is, inevitably, the wedding, yet Jim and Michelle are pushed aside in favor of countless Stifler antics. Jason Biggs and Alyson Hannigan made a wonderfully charismatic team in the previous two features, but here share too few scenes together to be lastingly effective. Hannigan's Michelle, the best thing about the series, has been softened to the point of rarely being given a good one-liner or character scene. Mostly, she stays in the background—something Michelle never did in the first two. Hannigan is an excellent actress, severely underrated, and she deserves better. For that matter, so does Thomas Ian Nicholas (2002's "Halloween: Resurrection"), given nothing satisfactory to do as Kevin.

The biggest flaw on director Jesse Dylan's (2001's "How High") part is in handing over lead role duties to Seann William Scott (2003's "Bulletproof Monk"), as Stifler. Scott, another standout of the first two movies with his showy supporting part, wears out his welcome quick as the lead, and hasn't smoothly drifted back into Stifler's shoes. Something feels very off about Scott's performance here, and his facial expressions sometimes border on creepy when that clearly wasn't the actor's intention. What does work is his romance with Michelle's free-thinking sis, Cadence. January Jones (2003's "Anger Management") makes for a bright, earthy counterpart to the more out-there Stifler. Also making requisite appearances are Eugene Levy (2003's "A Mighty Wind") as Jim's faithful dad, and the invaluable Jennifer Coolidge (2003's "Legally Blonde 2") as Stifler's Mom.

"American Pie" and "American Pie 2" blended smoothly together, a beautifully crafted rites of passage duo that were always funny, but not afraid to remain honest about friendships and romance. In comparison, "American Wedding" feels tired and empty, a motion picture with a handful of fine moments surrounded by one missed opportunity after the next. And despite Jim and Michelle's climactic dance to The Wallflowers' cover of "Into the Mystic" recapturing the pure magic of their loving relationship, it does not excuse the fact that they are otherwise shortchanged throughout. Making Stifler the star was a bad idea; a loud and over-the-top creation like him is perfect for a supporting role, but grates on the nerves when onscreen for longer portions. It doesn't take a rocket scientist (or a pie fornicator) to tell that "American Wedding" is easily the weakest in a once-promising series.