The idea that Barbra Streisand might have given birth to Seth Rogen actually makes a twisted kind of biological sense, but it prompts one to wonder: Who on earth was the father? Zero Mostel? Fozzie Bear? Sadly, “The Guilt Trip” doesn’t speculate upon matters genetic. Whoever Dad was, he has been peacefully dead for years and Mama Streisand has been on High Noodge ever since.

The movie’s silly, predictable, and surprisingly sweet — the sort of thing you can and probably should take your mother to. Rogen plays Andrew, an organic chemist (not a doctor, but close!) who has invented a nontoxic cleaning product and is taking a road trip across the country to shill it to chain stores like Kmart and Costco. The product is called Sci-O-Clean, its packaging is more cluttered than Dr. Bronner’s, and Andrew has the showmanship of, well, an organic chemist.