It’s hard to know exactly who “Parental Guidance” was made for.

With a script that relies heavily on gags about vomiting, urinating and defecating — and that includes not only a crack about “melons” as a euphemism for breasts, but a shot of Billy Crystal getting hit in the crotch with a baseball bat — this generation-gap comedy about grandparents taking care of bratty grandchildren seems like it’s not just made for children, but written by one. On the other hand, stale jokes about sciatica and the cluelessness of the elderly when it comes to tweeting and other forms of modern technology seem like they popped out of the VCR in the old folks’ home.

The answer is that the movie is perfect for families. Assuming, of course, that: a) your family has traveled in time from 1995, when most of the jokes in the movie were first written; b) you have absolutely nothing better to do over the holidays; and c) you have no taste whatsoever.

“Parental Guidance” is not just dull; it’s aggressively dull, as if the people who made it actually want to put you to sleep and then steal your wallet. (Check your pants before you leave the theater.) It’s also badly overacted, syrupy, phony looking, implausibly scripted, formulaic and about 15 minutes too long.

When yuppie parents (Marisa Tomei and Tom Everett Scott) go out of town for a few days, they decide to leave their brood of three spoiled crumb-snatchers (Bailee Madison, Joshua Rush and Kyle Harrison Breitkopf) with the grandparents (Billy Crystal and Bette Midler). What ensues is exactly what you would expect: disaster involving cake frosting on the face and apoplectic mugging, followed by scenes of saccharine reconciliation so insincere they make Crystal’s dye job and Midler’s facelift look natural.

The normally wonderful Tomei acts, with broad cartoonishness, as though she has wandered off the set of a Nickelodeon sitcom. The three juvenile actors behave more like animatronic figures than real human beings. And Midler and Crystal (who also produced the film) are mired in a tar pit of schtick, like Borscht Belt dinosaurs.

Little more remains to be said about “Parental Guidance,” except this caution: No one should be allowed in the theater, even with the accompaniment of a parent or adult guardian.

PG. Contains juvenile humor about bodily fluids and body parts. 105 minutes.