In the course of being relentlessly and criminally cute, the young lovers in tonight's CBS movie "Happy Endings" throw pies at each other in a public park, let a car smash into trash cans on a San Francisco curb, throw garbage about on a city street, and toss unwanted belongings--like record albums and panties--into the bay beneath the Golden Gate Bridge.

If nothing else, this snickery pair ought to be arrested for littering, but they have other offenses up their precious little sleeves. The film, at 9 on Channel 9, is a wrong-note samba from first winkie-poo to last. "You're always so glib," snaps the young woman to the young man. "I am not glib," he retorts. "I'm superficial." That isn't the half of it. That's the whole of it.

John Schneider, whose return to "The Dukes of Hazzard" last Friday was certainly a turning point in the annals of Star Power, is miscast here as a perspiring novelist who answers the phone with a chipper, "Hello--Nick Callohan, writer." There's no way this strapping blondie could be mistaken for an author of anything but a bad country-western tune. Catherine Hicks, who played Marilyn Monroe in ABC's film biography a few years ago, tries her best as Schneider's feisty heartthrob, but the script, by Christopher Canaan, makes the character a fey, tiresome kook, the kind of part that would normally go to Didi Conn or someone else mighty icky.

The story has the pair meeting as both are coming off unhappy love affairs with others. Throughout the film, he keeps thinking he's going back to his old amour, and she keeps thinking she might go back to hers, and then they don't, and then they do, and then they realize they really love each other, but then he tries to tell her and doesn't, and she tries to tell him and doesn't, and at no point is a viewer induced into caring whether these kitty cats ever stop pussyfooting around or not.

Noel Black, the director, made the cult film "Pretty Poison," with Tuesday Weld, many years ago, and now is working in television. He doesn't do enough to lower the saccharine count of the script. Schneider and Hicks are both immensely personable, but all the Barrymores put together couldn't bring credibility to "Happy Endings," clearly wan lark too many.