"Trading Places," a fiscal fable with Eddie Murphy and Dan Aykroyd, is bullish on comedy -- your five-dollar investment returns a million yuks.

John Landis ("National Lampoon's Animal House") directs this 1980s American Dream of a movie, with Murphy as "My Fair Lady" twice removed, and Aykroyd as first prince, then pauper, but mostly a pawn of billionaire brothers played by Ralph Bellamy and Don Ameche.

For comic superstars Murphy and Aykroyd it's an exchange of pace: Murphy plays ghetto-hustler Billy Ray Valentine, and Aykroyd is commodity whiz Louis Winthorpe III. Costar Jamie Lee Curtis, finally free from creep shows, joins them in taking a lick at the silver spoon. She's curvacious and vivacious as a hooker who takes Winthorpe in when he's supplanted by Valentine.

It's all for a dollar bet between Bellamy and Ameche, who engage in an ongoing quarrel over whether breeding or environment make the man. "Given the right surroundings, that man could run our company as well as young Winthorpe," one says of Valentine, who has just been arrested in their blueblood club. They enlist Winthorpe's butler (Denholm Elliott) in their implausible swap, which the butler, our two heroes and the hooker turn into a vengeful sting.

It's a flawed film, but Murphy makes the most of every moment, proving that his first effort, "48 Hours," was no fluke. He's a blue-chip funnyman, whether he's zinging preppies or students from Cameroon. Aykroyd, with a hit film at last, mostly plays it straight, except when he throws a drunk scene in a Santa Claus suit and a pair of white pumps. The two enjoy a partnership far and away less explosive but no less enjoyable than the one between the late John Belushi and Aykroyd.

Belushi's brother James has a bit part as King Kong in this crazy-quilt cast -- a colorful collection of players that includes Bo Diddley as a pawn broker, Frank Oz (voice of Miss Piggy and Yoda) as a tough precinct cop, and Franken and Davis as gorilla keepers.

"Trading Places," with its injection of old- fashioned optimism and simple-minded philosophy, isn't subtle stuff. But that's not its stock in trade. It seems to say that Horatio Alger isn't dead, but rather in the black. TRADING PLACES -- At area theaters.