IT MAY have something to do with my sons Alexander and Adrian, who are never afraid to take precious time away from their studies for meaningful moments with "South Park," "Beavis and Butt-head" and Adam Sandler movies. I, too, have learned to appreciate America's comic bottom feeders when I could be, say, doing the laundry or filing medical health forms.

This would explain why I laughed aloud when Sandler -- in that strangled falsetto of his -- parodied Whitney Houston's "I Will Always Love You" in the otherwise throwaway movie "Bulletproof." This would explain why I was one of possibly 11 adults with a job who actually looked forward to "The Waterboy."

I got the real lowdown. I know my bad from my bad. So take me seriously when I say the Sandler mojo ain't working in "Big Daddy." No siree Bob. Dismal. Lame. Not funny.

In fact, this comedy, which Sandler produced, co-wrote and stars in, has some of the worst writing I've seen in an Adam Sandler picture. There are Pauly Shore movies funnier than this. If those aren't insults, I don't know what are.

It's not the gross stuff that bothers me. Examples: Sandler -- who plays 32-year-old slacker supreme Sonny Koufax -- relieves himself frequently alongside his new 5-year-old charge, Julian (Cole and Dylan Sprouse). He also teaches the kid how to dangle a long, slimy string of mucus from his mouth almost to the sidewalk then slurp it back.

But if anything, those are the highlights. The problem is the unwriting, as performed by Sandler and fellow writers Steve Franks and Tim Herlihy.

Here's the story, such as it is: Sonny, who's done nothing with his law school degree (in other words, he knows he's set, no matter how much he messes up), spends his days sleeping or watching New York teams -- Rangers, Jets, whatever -- on the tube. Understandably, his girlfriend Vanessa (Kristy Swanson) tells him to get his act together or forget everything.

An opportunity to bring back Vanessa presents itself when Sonny gets a call from the city's social services agency. Seems that Sonny's law school buddy Kevin (Jon Stewart) sowed at least one wild oat that got harvested. A 5-year-old kid called Julian is suddenly in need of a father or he's going to the orphanage. Mom, you see, is dying of cancer. Are we having fun yet?

Sonny figures Kevin doesn't even want to know about this. He also figures, if he adopts the kid, it'll impress Vanessa. She'll see his paternal side and come running back. Or something like that.

Vanessa dumps him anyway. And Sonny, who wouldn't know parenting if it wielded a hockey stick, finds himself stuck with a boy who wets the bed, needs someone to pee next to him, has problems falling asleep and loves listening to an irritating children's video. The agency says they'll take the kid back when they find a suitable foster family. In the meantime, Sonny agrees to hold on to Julian.

Enough plot already. The fact is, here's an opportunity for big brat-little brat comedy. It just doesn't happen. Everything seems about one comic beat off. Sonny teaches Julian to stick a log in a strategic spot so Rollerbladers will fall. Yuk, yuk, yuk! He teaches the kid to say "The [expletive] Jets!" What a riot! And whenever Julian makes a mess on the floor or in bed, Sonny throws a newspaper over the offending patch. Stop, please, my sides are splitting!

To fulfill the love interest, along comes Layla (Joey Lauren Adams), an attorney who comes to appreciate Sonny's sloppy adorability. She even helps him put Julian to bed with a cutesy storytelling duet -- something about squirrels and rabbits getting to know each other and having a really good relationship. By this time, surprise, surprise, Sonny's starting to like the little mite -- even though neither of the twins who play him can act very well. In fact, the Sprouses are so bad at crying, director Dennis Duggan (whose credits include Sandler's "Happy Gilmore" and "Beverly Hills Ninja") has one of them turn his back to the camera when he sobs.

There are one or two laughs. How could there not be? My personal favorite came from Steve Buscemi, who plays a zoned-out homeless person, who tries to explain his homeless, zoned-out status. During the disco era, he explains, he did a lot of hallucinogenic mushrooms and watched "Fantasia" a lot. "In retrospect," he deadpans, "I made some really bad decisions after high school."

Rob Schneider, who plays Sonny's delivery-man pal, is not particularly amusing. Sonny has two gay lawyer-friends who spend the entire movie gazing adoringly at each other or deep-kissing each other. It's unclear whether the movie is applauding gay rights or finds this behavior amusing. The movie obviously finds it hilarious that Kevin's snotty fiancee Corinne (Leslie Mann) used to be a waitress at Hooters. Sonny constantly makes "cracks" about this, even though, when Julian needs a night light, the 32-year-old pulls out a Live Nudes neon sign from his room. Let's see, Corinne's a slut because she worked at a place where, presumably, Sonny goes all the time? I guess I had a problem with the, uh, moral argument. In fact I guess I had a problem with almost everything. Clearly, it's time to re-rent "The Waterboy."

BIG DADDY (PG-13, 95 minutes) -- Contains obscenity, suggestive language and some slapstick violence. Area theaters.

CAPTION: Bad writing takes its toll on Adam Sandler and Cole (or Dylan) Sprouse.