Lowbrow comedy goes subterranean in “That’s My Boy,” a product of the Adam Sandler movie factory unpolluted by a trace of ambition or wit.

This film forgets that good comedy is rarely dumb — it just plays dumb. Sandler, treading water in a sea of bodily fluids, retarded sexuality and antisocial behavior, makes you yearn for the rib-tickling sophistication of “Ernest Goes to Camp.” The movie should be buried in a time capsule to teach future generations what to avoid.

The deluxe-stupid script positions Sandler as Donny, a washed-up minor celebrity who rocketed to national fame when he impregnated his red-hot math teacher at age 13. Now he’s a beer-bloated, middle-aged man-child who needs his successful adult son’s financial help to avoid a prison sentence for tax evasion.

The boy (Andy Samberg), whom he christened Han Solo, changed his name to Todd and severed all ties for reasons that should be obvious. On Todd’s wedding weekend, Donny re-enters his life, wreaking havoc at every turn.

As he has done before, Sandler makes his character a babe magnet. Sad sack Samberg is Donny’s mirror image. He’s the poster boy for mousy repression — his pretty, domineering fiancee is obviously interested in the rising executive for his money alone — and when Dad grasps the situation, he changes his mission, deciding that a good, gutter-wallowing hookers-and-booze bachelor party is what his dweebish boy needs. Cue the urine and barf jokes.

If this summary is unpleasant, I assure you the film is a lot more fun to read about than to endure. It is about as funny as watching an obese stripper eating an omelet while upside down on her dance pole. Which they actually show.

As you would expect, the standard Sandlerisms repeat themselves. Surprise Star Cameos drag a veritable Who’s Who of familiar faces out of retirement and repurpose them as objects of our derision. Why else cast Tony Orlando in a supporting role that requires him to wear the world’s ugliest toupee?

The mix of hackery and self-regard on display here is amazing. The film is the work of professionals who do have the resources to make a well-constructed comedy. They simply don’t respect their audiences, or their craft, enough to make the effort.