Maybe it's my imagination, but I think Barry Manilow must have bounded into the CBS offices sometime last year and warbled, "I know you're worried about network ratings. I've got a swell idea. Let's put on a show!"

How else could the Mickey Rooney of rock have conceived such a gosh-darn root beer float of a film, "Copacabana," a two-hour musical comedy showing tonight (Channel 9 at 9) that might be the longest, lushest video ever made.

Based on Manilow's 1978 hit record of the same name -- a tune so catchy it should be illegal -- "Copa" is so dopa it's darn near perfect. Maybe it's my imagination, but it's been a long time since something so upbeat has burst into our living rooms, leaving out the last Smurfs special. It's so inoffensive you'll forget you're watching a movie of the week. Nobody gets AIDS. Nobody takes drugs. Everybody sings and dances, orders drinks with umbrellas in them and keeps his clothes on.

Manilow is cuter than a pet chipmunk in his white tuxedo and sings 10 catchy new songs. So what if they all sound like McDonald's commercials -- you were expecting Gershwin? As an actor, Manilow is no De Niro, and as a hero, he's closer to Rocky the Squirrel than Rocky I-IV, but he does have a certain presence and a beguiling, unselfconscious comedic style.

He camps it up as pianist Tony Starr, while Annette O'Toole (last seen as Tammy Wynette in "Stand By Your Man") vamps it up as singer Lola Lamar. The two make a fetching couple, although O'Toole's voice is often flatter than a tortilla. Joseph Bologna, as gangster Rico Castelli, cuts a menacing figure in his mustache and pinky rings. "The deadliest snake in the Western Hemisphere," Bologna alone-ya is worth the price of admission. Estelle Getty (currently wowing audiences as one of "The Golden Girls") does a nice turn as Manilow's Jewish mom and Silvana Gallardo is delightfully wacky as the tart-tongued Spanish spitfire Conchita.

The story, as told in flashback, is a glitzy rehash of the standard '40s boy-meets-girl musical. Tony meets Lola while both are contestants on "Sing That Tune." He wins an engagement at the Copacabana. Unfortunately, the only opening is behind the bar. He tries to work his way up to lounge lizard while Lola fends off advances from customers at a nearby dance hall and gets in hot water with her boss. ("He is Prince Charming, and you're Cinderella and this is the Glass Slipper. Get it? Get it or get out.")

One night at the Copa, the kids get their big break when the pianist falls down drunk. O'Toole belts out a zippy little number, "Man Wanted," with Manilow on the ivories. "Keep your gents from Lord & Taylor, slip me one good sweaty sailor . . ." Is that a Copa girl? Ay, Caramba!

Things look rosy until Rico (owner of the Tropicana nightclub in Havana) spots Lola in the Copa chorus line. What does he see in her? "Purity, chastity . . .I'm gonna revive El Bravo."

She: "What's El Bravo?"

He: "Only the greatest number in the history of the Tropicana, maybe in all nightclub history. A pirate ship right in the middle of the stage. A swarm of pirates and pirettes."

She: "Pirettes?"

He: "Girl pirates. Formerly virgins. Captured and converted by the pirates."

When Rico entices Lola down Havana way, Tony turns to wealthy divorce' Pamela Devereaux (Andra Akers) for comfort. With her help, Tony decides to rescue Lola from Rico's clutches and from the curse of the Star of the Caribbean, a fatal diamond ring the size of a skating rink that Rico has slipped on her finger.

You'd think all this harmless fizz would guarantee a happy ending. It doesn't. But thanks to producer Dick Clark and lyricists Bruce Sussman and Jack Feldman, Manilow has managed to breathe new life into the tired variety-show format. There is much to recommend in this big-budget production: The photography is first-rate, the smoky cafes and rain-swept streets a haunting backdrop for the lush string section; even the showgirls look as though they're having fun.

At the Copa, who could ask for more?