"Along Came Polly" should be a better film than it is, it really should. On paper it has every advantage, from gifted stars Ben Stiller and Jennifer Aniston to an established comedy writer-director with a promising idea about a romance between a carefree woman and a worried man. But instead of maximizing those pluses, "Along Came Polly" so completely fritters them away that even its brief 90 minutes feels unhappily long.

"Polly" is all about Reuben Feffer, a man as timid as his name. A proud member of the National Assn. of Underwriters and a risk assessor for a major insurance company, Reuben never met a chance he was willing to take. It's a role that is practically custom-tailored for Stiller and his arsenal of concerned and troubled looks.

John Hamburg, "Polly's" writer-director, has had experience writing for the actor, all of it good. He co-wrote two of Stiller's funniest films, "Meet the Parents" and "Zoolander," but this is his first time solo writing and directing since his debut with "Safe Men," a 1998 Sundance entrant. It's not a promising return. For this film makes it clear that the ability to think up characters and even come up with funny lines is not enough. "Polly" is a hit-and-miss affair with more flat moments than comic ones. Burdened by clumsy plot threads, a confusion of tones and a weakness for bathroom humor, it never gathers enough momentum to compensate for all those drawbacks.

We meet New Yorker Reuben doing what he does best — worrying — on what should be the happiest day of his life, his wedding to the beautiful Lisa Kramer ("Will & Grace's" Debra Messing). Maybe the floors are too slippery for the 23% of the guests who are over 70, but this woman is Reuben's definition of the perfect mate. A honeymoon on St. Bart's does not, however, turn out as planned, and Reuben finds himself back in Manhattan hanging out with his oldest friend, Sandy Lyle (the invariably satisfying Philip Seymour Hoffman), a former teen movie star now reduced to playing both Jesus and Judas in a community theater version of "Jesus Christ Superstar."

Dragged to a party by Sandy, he runs into Polly Prince (Aniston), an old middle-school pal who once upon a time was Reuben's co-delegate to the Model U.N. Now, however, waitress Polly is more likely to see the world than represent it: She's lived everywhere from Sri Lanka to Costa Rica to Portland, and she is so averse to planning and commitment it's hard for her to say yes to a simple dinner date.

A believer in destiny, Reuben is convinced that Polly is the new girl for him. But while there's a clear potential for humor in this relationship, writer-director Hamburg seems to have lost the instinct for how to find it.

For one thing, though Aniston is charming in the role, her Polly feels more like a construct cobbled together from random character traits than a person as real as Reuben. Even more contrived to make obvious plot points about the importance of living life to the hilt is the film's main subplot, Reuben's attempt to decide whether daredevil businessman Leland Van Lew (Bryan Brown) is too risky to insure.

"Polly" takes a serious turn when we least expect or want it. And its overreliance on extended bathroom-humor scenarios is not only not funny, its prominence is at variance with the more-or-less adult tenor the rest of the plot is attempting. And don't even ask about the persistence of blind ferret jokes.

If you've seen "Meet the Parents" and "Zoolander," you won't be surprised that "Along Came Polly" does have its moments, and the versatile Hank Azaria as a French scuba god is especially funny. But overall this film is not in the same league as its predecessors. Comedy collaboration is derided at times in our auteur-obsessed age, but it's got a batting average that going it alone can't always match.

'Along Came Polly'

MPAA rating: PG-13 for sexual content, language, crude humor and some drug references

Times guidelines: Considerable bathroom humor

Ben Stiller ... Reuben Feffer

Jennifer Aniston ... Polly Prince

Philip Seymour Hoffman ... Sandy Lyle

Debra Messing ... Lisa Kramer

Alec Baldwin ... Stan Indursky

Hank Azaria ... Claude

Bryan Brown ... Leland Van Lew

A Jersey Films production, released by Universal Pictures. Director John Hamburg. Producers Danny DeVito, Michael Shamberg, Stacey Sher. Executive producers Jane Bartelme, Dan Levine. Screenplay John Hamburg. Cinematographer Seamus McGarvey. Editors William Kerr, Nick Moore. Costumes Cindy Evans. Music Theodore Shapiro. Production design Andrew Laws. Art director Martin Whist. Set decorator Don Diers.

Running time: 1 hour, 30 minutes.

In general release