Scoff if you wish, but take it from me. "Sex Drive" is an unexpected gem, a ridiculous thing of beauty. Sure, it's juvenile, crass and formulaic. What do you expect from a movie about horny teens on a cross-country quest to lose their virginity? What matters is that it brings a welcome intelligence and an ensemble of really cool, funny actors to the age-old subject manner.

Josh Zuckerman plays Ian, a Chicago teen whose dating life consists of Internet flirtations, where he can PhotoShop his head on a buff football hero's bod and boast about his brother's classic '69 Pontiac GTO as if it were his own. His virtual romance is with Ms. Tasty, whose online profile is a blonde hottie living in Knoxville. She messages him invitations like, "U Drive All the Way Here 4 Me ... I'll Go All the Way with U," and the plot is set in motion with a minimum of wasted effort. Along for the ride are Ian's platonic gal pal Felicia (Amanda Crew) and his suave love tutor Lance (Clark Duke, putting a sarcastic Bill Murray topspin on his lines). Although he's a tubby guy with glasses and a baby face, Lance exudes such improbable confidence that women flock to him, one of the film's many engaging character twists.

Hurdle No. 1 on Ian's cross-country journey to manhood is big brother Rex (James Marsden, "Enchanted," "Hairspray"), the most tyrannical sibling since Bill Paxton in "Weird Science." He's actively invested in making Ian miserable, whereas their 14-year-old little bro just humiliates Ian in passing, surpassing him in the makeout department. Even Ian's job at the mall pastry stand undermines his ego as he hands out coupons in a doughnut costume that makes him look like a giant zero. Clearly, Ian has to restore his confidence with a pedal-to-the-metal road trip to Tastyville. While Rex is out of town on a family vacation, Ian will borrow his car and return it a couple of days later, with no one the wiser.

That's the plan anyway. You can probably foresee some of the complications, from roadside breakdowns to romantic complications when Ian and Felicia have to renegotiate what it means to be BFFs. The surprises of the film are how lovable the characters are and the distinctively daft comic sensibility that guides it all. Zuckerman and Crew have a delightful everydweeb quality, touchingly funny and believably clueless about their own feelings. The screenplay is agreeably raunchy, but the players react so casually to the wicked material that it ratchets the humor up another notch. The script is full of time-released jokes that detonate at just the right second, and recurring minor characters that are funny enough to star in their own movies. The standout is comedy god Seth Green as Ezekiel, an Amish good Samaritan who lends a hand when the muscle car dies. By tiny degrees Ezekiel emerges as the most sarcastic, passive-aggressive and manipulative member of the brethren imaginable. His dialogue is deliciously cynical, but Green's bizarrely brilliant line readings make it uproarious.

Although the film is essentially sketch-based -- there are sequences set at a raunchy state fair talent show, a gaudy fantasy suites motel, a couple of jail cells, a trailer park love nest and a boozy Amish kegger featuring Fall Out Boy in concert -- there's a narrative consistency that makes it all cohere. The story is carefully structured, unlike so many comedies that race off in 11 wrong directions at once. Director Sean Anders has an impressive grasp of visual comedy too. He knows how to stage funny background action, the importance of concealing a gross-out sight gag for maximum surprise, and how to make falling down look novel. At its core, though, "Sex Drive" is about people and their absurd desires and their failings: It's human comedy in the truest sense.

Colin Covert • 612-673-7186