Who would have thought it? The idea that a picture starring David Spade, surely one of the most irritating of the Saturday Night Live castoffs to wind up on the big screen, could be pleasant, even rather sweet, seems absurd; but that’s what happens here. “Dickie Roberts: Former Child Star” is like Spade’s version of “The Wedding Singer”–a movie that might actually appeal to people who’ve previously found its star insufferable.

The premise of the picture isn’t promising. In a blatant ripoff of Adam Sandler’s “Billy Madison”–something that’s especially obvious since this is a Happy Madison production–Spade plays the unemployed thirty-something version of a kid who was all the rage on a seventies sitcom. He’s desperate to land the lead in a Rob Reiner flick to revive his career (even though Reiner’s recent track record hardly suggests that would be the result), but the director (in one of his stock guest appearances) doesn’t think he’s right for the part because he’s never had the experience of a normal childhood to fall back on. So Dickie rents a “typical” family he can live with for a month and rectify the omission. It goes without saying that though he’s initially a difficult guest, eventually he bonds with mom and the two darling kids (though dad is quite another story). And of course he learns there are more important things in life than screen success, although–in typical sitcom fashion–he manages to get both.

Nothing special there. And it must be said that the movie’s opening scenes–involving a celebrity boxing match against Emmanuel Lewis and Dickie’s abandonment by his snotty girlfriend (Alyssa Milano)–hardly inspire confidence, allowing Spade’s usual annoying tics free rein. But things pick up quickly when Jon Lovitz enters the picture as Dickie’s harried agent and the two concoct the plan to send the desperate guy forward to the past; Lovitz’s unctuous, ineptly scheming persona works perfectly here. And the family Dickie ultimately winds up with–mom Grace Finney (Mary McCormack) and kids Sam (Scott Terra) and Sally (Jenna Boyd)–turns out to be a likable trio. To be sure, a good many of the bits–the obligatory slapstick disaster as Sam and Sally teach Dickie how to ride a bike or play slick and slide, or the run-ins with a hostile neighbor (Edie McClurg)–are extremely predictable, but the chemistry between Roberts and the Finneys saves more of them than you’d expect. And then there are the self-mocking appearances by real kid stars like Barry Williams, Leif Garrett, Corey Feldman, Dustin Diamond and Danny Bonaduce that, amazingly, turn out to be both funny and warmly nostalgic. (The one who gets the most screen time is Garrett, who’s so pleasant you might even be able to forget the notorious VH-1 “Behind the Music” episode dealing with him.) Even more once-popular names show up for a group sing under the final crawls; this is one of the few instances when it really pays to sit through the closing credits.

“Dickie Roberts” is hardly a masterpiece–the script, after all, is by the same Spade and Fred Wolf who wrote “Joe Dirt,” and some of its gags are badly conceived (the younger Dickie’s famous catch phrase, for example, is no great shakes the first time you hear it, and it’s repeated far too frequently). Sam Weisman’s direction is at best workmanlike. Milano, moreover, is sadly shrill, and Craig Bierko stumbles badly in the poorly-written role of the money-hungry, unscrupulous George Finney. But the movie is a surprisingly good-natured, winning bit of family fluff. It probably won’t change its star’s image, but it may well make more viewers willing to give him a chance.