Juno, a bittersweet 16, is named for the Roman goddess of fertility. Had she time to reflect, the smartmouth might snark that the unusual name foretold that she'd be a "fertile Myrtle," conceiving the first time she had sex. But the Minneapolis high school junior is too busy chugging SunnyD and juggling choices. Abortion? Teen motherhood? Adoption?

An improbably endearing comedy about a decidedly unfunny situation, Juno marks the sparkling screenwriting debut of Diablo Cody, the distinctive sophomore effort of Jason Reitman (Thank You for Smoking) and the breakthrough performance of a 5-foot acting giant named Ellen Page.

Don't let her Bambi eyes and button nose fool you, motormouth Juno (Page) enjoys shocking people. The biggest shock is hers when she recognizes that a know-it-all attitude doesn't mask ignorance, a freewheeling banter doesn't cloak insecurity, and her outsider status doesn't sentence her to a lonely life.

Like its heroine, the film's glib - and sometimes sidesplittingly funny - patter at first diverts viewers from its poignant insights. Happily, as Juno grows in experience and maturity, so does the film.

Abandoned by her mother and raised by Dad and Stepmom (J.K. Simmons and Allison Janney, as indescribably funny as they are moving), Juno is the poster girl for the changing American family, where ties of kinship are not necessarily genetic.

For this girl who chooses to carry to term, all but one of her most important relationships are para-familial. Juno's father is there for her, but no less essential are her stepmother, the potential adoptive parents (fragile Jennifer Garner and ironic Jason Bateman) and Bleek (Michael Cera), whom she might archly refer to as the fetus' father. She also has a support best bud, Leah (Olivia Thirlby).

The film spans the three trimesters and four seasons during which Juno evolves from teen misfit to the cusp of adulthood. Reitman carpets the soundtrack with wall-to-wall alt.music, much of it by Kimya Dawson of the Moldy Peaches. That these plaintive tunes are so self-conscious underlines Juno's state-of-mind.

What moved me most about the film was its sympathy for its characters as well as its belief that the time to make up your mind about people is never.

This is a nonjudgmental movie about a heroine with the poor judgment to engage in unprotected sex. Yet screenwriter Cody (born Brook Busey) understands that characters are not predictable, not even the yuppie couple "desperately seeking spawn" who want to adopt Juno's baby, and with whom she seeks to resolve her conflict about not having an intact family.

Led by Page, who has the spitfire presence of the young Holly Hunter, all the performances are surprisingly touching. While it's a near-certainty that Page will get an Oscar nomination for lead actress, it's a distinct possibility that Simmons, Janney, Garner, Bateman and Cera will all bag supporting nods.

Yeah, it gives me a minute's pause that the takeaway message of this tasty farce might be that an unplanned pregnancy is a maturing experience. I don't think that is the intention of the filmmakers.

But what I took away is that - bio-, step-, or adoptive - there are as many kinds of love as there are kinds of families as there are kinds of parents.

And what kind of movie is Juno? The rarity that plucks your heartstrings while tickling them.