Former-stripper memoirist and publicity magnet Diablo Cody scripts a distinctive contribution to the comedy-of-unwanted-pregnancy subgenre (see also Knocked Up), which limns Gen-X legacy anxiety with sass and sarcasm and verbal dexterity—sometimes at its own peril. Her vessel is the eponymous intelligent, irreverent, accidentally pregnant 16-year-old played by Ellen Page, who absolutely owns the material. She also marshals an army of supportive straight men, from the moneyed yuppies whose prayers of parenthood Juno answers (Jason Bateman, Jennifer Garner) to her own good-humored parents (Allison Janney, J.K. Simmons) to her gangly-sweet, unreasonably patient impregnator (Michael Cera). Director Jason Reitman makes his presence felt by framing the film with standard indie-quirk trappings but otherwise just gets out of the actors’ way. The real feeling of the thing, though, its Gilmore Girls-for-alternateens tone, is all courtesy of Cody. Brace yourself for the uncontrolled population of her imitators.