John Goodman proves himself a terrific comic actor in his first lead role as "King Ralph." But the script and direction, by David S. Ward - yes, the same guy who won an Oscar for writing "The Sting" in better days - never rises above sitcom level.

Still, Goodman invests an awful lot of charm in the role while demonstrating an adroit knack for slapstick and the wide-eyed doubletake, which makes the film less than the embarrassment it might have been in the hands of, say, John Candy. (And if ever a script seemed tailor-made for Candy, this is it.)Unless you've been vacationing on the moon, you've probably seen a "King Ralph" TV ad and know that the plot spins around the entire royal family being wiped out in the film's first scene.

So Great Britain plunges headlong into genealogical research in an effort to track down an heir to the throne - any heir - finally settling on a loutish American, a Las Vegas lounge singer named Ralph Jones (Goodman).

This happens fairly rapidly so the film can get down to the business at hand - namely the fish-out-of-water plot that has "King Ralph" being trained in royal etiquette, which is no easy task. Ralph must learn to give speeches, meet dignitaries from other countries and eventually is even led into an arranged marriage. But he keeps his down-home values by installing a bowling alley in Buckingham Palace and has a ferris wheel placed on the grounds.

Though obviously a one-joke film, "King Ralph" nonetheless contains some amusing ideas. But Ward exhausts them fairly quickly and then relies on less inventive jokes that range from the predictable (Ralph playing cricket as if it's baseball) to the childish (Ralph's fiance is kept quiet until she is eventually revealed to have a very silly voice) to the tasteless (Ralph trying some jive talk with an African king).

Speaking of tasteless jokes, how about the gag concerning the British dessert "spotted dick" - which is used not once but twice! And parents who take their children will be chagrined at the vulgar, unnecessary moment in a strip joint, which seems deserving of at least a PG-13!

There are several supporting players who deserve more to do - including John Hurt as a conniving would-be monarch. But the only two who get an opportunity to display their charms are Camille Coduri as the commoner Ralph falls in love with and especially Peter O'Toole as the assistant who helps Ralph learn the royal ways. O'Toole's deadpan humor gives the film as a whole a frequent boost.

But what really saves "King Ralph" from disaster is John Goodman. He is very funny, lends some depth to the character and is a knockout in his showstopping "Good Golly Miss Molly" number.

It's just too bad his enormous comic gifts couldn't be better served.

"King Ralph" is rated PG for nudity in a strip joint, vulgarity, profanity and minor violence.