“Juno” has the right ingredients to take it from a modestly scaled comedy-drama to a huge hit on the order of “Little Miss Sunshine.” Among them are originality, a big heart, an off-beat sense of humor and likable characters.

The most likable character is the one who gives the movie its title.

Juno is a 16-year-old high school girl. She and her friend, Bleeker, decide to divest themselves of their virginity and recklessly don’t use contraceptives. This is a story about facing the consequences of one’s actions and in this case those consequences are profound. Juno finds herself pregnant. She considers an abortion and then discards the idea after a visit to the clinic. She will keep the baby and give it up for adoption. Her best friend Leah suggests the want ads and Juno soon settles on what appears to be a suitable couple looking to adopt.

The Lorings, Mark and Vanessa, are a suburban couple with Yuppie written all over their house and wardrobe. Vanessa is kind of bossy and desperate to have a child. Mark has an edgy past that Juno relates to. He’s a musician and a horror movie fan like Juno.

During the process of her pregnancy, Juno feels growing pains as well as labor pains. Disillusion, disappointment, emotional turmoil and the unpredictability of life assail Juno. But, as wonderfully played by Ellen Page, Juno has the strength and the humor to stand tall. Page’s performance is as endearing as any in memory. She can snap off a funny line beyond her years with the kind of surface bravado that lets you see the vulnerability underneath. Juno’s wit is her self-defense but her eccentricity and intellect come from her core, not from some kind of pose.

The other characters are spot-on, as well. Michael Cera, as Bleeker, the baby’s father, is a likable, low-key semi-geek. J.K. Simmons and Allison Janney, as Juno’s parents, provide strength and love instead of anger and disapproval: they don’t waste time with hand-wringing and instead roll up their sleeves to get Juno through her ordeal.

Juno’s best friend, played by Olivia Thirlby, is an oddity in movies about teens — a cheerleader with brains and a good soul. Jennifer Garner as the adoptive mother is especially good and Jason Bateman as the adoptive father provides the right read on a grown-up pining for youth.

Writer Diablo Cody, a former stripper, gives the movie its trenchant dialogue, vivid word imagery and sense of everyday absurdism. Even though the writing seems self-conscious at times, it still remains original and funny. Finally, director Jason Reitman settles on a whimsical tone and lets the writing and the actors run with the movie.

“Juno” seems not to be a message movie about teen pregnancy but a slice-of-life story about how a certain group of people handle it. In this case, they do it with love and humor and an acute awareness of the pain and uncertainty that come with the territory.