BY GLENN WHIPP >FILM CRITIC

The coming-of-age comedy "Juno" begins with the Sunny Delight-swilling heroine of the title taking several home-pregnancy tests at the neighborhood drug store before finally accepting that she is, in the words of the year's other unplanned pregnancy comedy, knocked up.

"This is one doodle that can't be undid, home skillet," Rainn Wilson's smart-mouthed pharmacist tells her from the counter.

What strikes you at first about "Juno" isn't the plight of this precocious teenage girl but the fact that everyone around her - dad, best friend, drug store guy - speaks in the same sing-song, precocious manner. You wonder: Does the local high school offer a required class in glib, mannered dialogue? And if so, why doesn't anyone escape before becoming one of the Pod People?

One of the surprises about "Juno" (and there are several good ones) is how the movie - directed by Jason Reitman ("Thank You For Smoking") and written by publicity magnet Diablo Cody - recovers from its early missteps and Wes Anderson aping and becomes a rather sweet comedy about a girl whose hip talk masks an aching vulnerability.

Juno (winningly played by Ellen Page) comes by her "doodle" courtesy of her shy, short-shorts-wearing, track-star friend (but not boyfriend) Bleeker (Michael Cera). After digesting the pregnancy test results, she picks up her hamburger-shaped phone (I know, I know) and calls the local abortion clinic. But disliking the place's "dentist office" vibe, Juno decides to carry the baby to term and put it up for adoption.

She finds the "perfect couple" in a PennySaver ad - Mark (Jason Bateman) and Vanessa (Jennifer Garner), an affluent, good-looking pair who, at first glance, seem a far cry from Juno's squarer, working-class parents (J.K. Simmons and Allison Janney).

But as autumn turns to winter and winter to spring, Juno's assumptions about these people - and herself - are upended, and the film gains a measure of composure equal to that of its heroine.

It helps to have a truly outstanding ensemble cast, headed by the self-possessed Page and the impossibly sweet Cera, and including a career-best turn from Garner and great work from "old-timers" Simmons and Janney, whose blunt wisdom balances the movie's motor-mouthed moments.

Credit, too, the filmmakers for self-awareness. When Juno tells Bleeker that he's "really cool without really trying," Bleeker looks at her shyly and replies, "I try pretty hard, actually." The movie does, too, but, by the end, you can't help but surrender to its considerable charm.

Glenn Whipp, (818) 713-3672 glenn.whipp@dailynews.com

 review>

JUNO

>PG-13: mature thematic material, sexual content, language.
>Starring: Ellen Page, Michael Cera, Jennifer Garner, Jason Bateman, Allison Janney, J.K. Simmons.
>Director: Jason Reitman.
>Running time: 1 hr. 31 min.
>Playing: ArcLight at Sherman Oaks Galleria; the Landmark in West Los Angeles; ArcLight in Hollywood; Pacific's The Grove Stadium 14 in Los Angeles.
>In a nutshell: Coming-of-age comedy goes from overly mannered to pretty special.