“Jeff, Who Lives at Home” could be just another quirky, abrasive and unconventional relationship comedy from the Duplass Brothers, the fellows who gave us “The Puffy Chair” and last year’s “Cyrus.” It starts with the assertion — by Jeff (Jason Segel), the title character — that “everyone and everything is interconnected in this universe.” You know, he says, like that life-altering (and daft) M. Night Shyamalan movie “Signs,” a film that’s become Jeff’s obsession.

Jeff is a pothead and a slacker, living in his mom’s basement. So there’s nothing unusual about his love for “Signs.” What is shocking is how “Jeff, Who Lives at Home” proceeds to make its case for Jeff, and for M. Night, in 82 brisk, goofy and touching minutes.

This new Duplass dramedy packs in a pickup basketball game, a mugging, endless sibling arguments (Ed Helms is Jeff’s paint salesman brother, Pat), a workplace “secret admirer” subplot that involves their long-suffering mom (Susan Sarandon, luminous), Pat’s troubled marriage to the miserable Linda (Judy Greer, in her best performance ever), a car wreck and car chase.

And then it turns on a dime and gives us 10 minutes so emotional and thrilling that you won’t believe what you just saw.

Jeff is a 30-year-old stoner wondering when he will meet his “destiny.” Believing so deeply that life is giving him “Signs,” he takes a wrong number from an angry man demanding to chat with “Kevin” as an excuse to follow any random person named Kevin that he runs across over the course of his day. That puts him on the basketball court in the wrong end of Baton Rouge, and into conflict with his irritated mother and irritating brother.

Pat, given a confidently hapless twist by Helms, thinks he has it under control. Cocky enough to buy a Porsche over the objections of his wife, self-righteously dismissive of any random thought that floats out of Jeff’s mouth, Pat has his worst day ever as he tries to figure out if his wife is having an affair.

Meanwhile, poor Sharon (Sarandon) “hates” her kids, but spends the day distracted by anonymous flirty messages on her computer, trying to decode them with her gal-pal Carol (Rae Dawn Chong).

It’s all presented in that deadpan Duplass Brothers style — abrupt zooms used for comic effect, silly, over-the-top sibling arguments followed by sentimental brotherly bonding. But “Jeff, Who Lives at Home” takes the Duplass art to a new, deeper place. Credit the cast or the characters tripping through well-worn situations and relationships, but this is far and away their best movie.

Confessions will be made, crises avoided or grappled with and destiny will be met before Jeff has ended his long, meandering day. And when it’s done, you may find yourself Netflixing “Signs” again. Because maybe, in this case, this stoner-savant is onto something. Maybe everything IS connected.