In Parental Guidance, Billy Crystal — the self-appointed spokesman for American comedy — is reduced to vomiting on a child for laughs.

A nonstop joke machine (Billy Crystal) and his equally overbearing wife (Bette Midler) are forced to spend time with their work-obsessed daughter (Marisa Tomei), son-in-law (Tom Everett Scott), and a trio of estranged grandchildren, all of whom have Dr. Kevorkian on speed-dial. The set-up seemed idiot-proof: stick a pair of technologically inept oldsters in a voice-controlled prototypical “Smart House” (it’s a Type-A A-frame), and watch the gags begin. Frank Tashlin did it without breaking a sweat, but all Andy Frickman (She’s the Man, You Again) does is break wind. Freaking Frickman quite literally places his camera (audience?) in a toilet. Is this man not embarrassed to take credit for what little direction there is?

And how far the mighty have fallen: Crystal, the self-appointed corporate spokesperson for American comedy, is reduced to vomiting on a child for laughs. Later, like the snake charmer using his voice as a laxative, gramps sits on the bowl — with his red-headed(?) grandson parked on his lap — singing, “Come out, come out, Mr. Doody.”

By the time it’s over, Billy and Bette have the kids buzzing on sugar, watching Saw films, and playing with guns. The tykes would have stood a better shot at life had they been raised by wild dingos.

Bonus: when was the last time you laughed at a score? The pathos-laden scenes between Billy and his stuttering grandson — backed by composer Marc Shaiman’s weepy-strings — are more amusing than any of the intentional jokes. It’s not fun, it’s not funny, and the fact that this thing is bankrolled by the family-friendly folks at Walden Media makes it even moreso. A mother lode of awful, destined to delight even the most jaded bad-film connoisseurs among us. As for the four-star rating, it’s there to punish those who only look at the numbers without reading the review.