MICHAEL KEATON stars in yet another '30s take-off -- "Johnny Dangerously," a hit-and-miss spoof of gangster movies that also features Joe Piscopo, Maureen Stapleton and Marilu Henner.

"Did you know your last name's an adverb?" asks Henner, playing the third sassy songbird to mollify a mob boss in so many weeks. Hers is an erudite one-liner, part of this film's anachronistic and outlandish amalgam of low and high humor, physical and verbal business, and malapropisms and "mooning" jokes.

Like most spoofs, it works till the joke gets old (about half way through) and then tedium prevails. But when it's good, it's really got the guffaws, drawing on such diverse influences as the bull malt liquor commercial and Cagney movie camera angles.

Keaton mugs Cagney and his counterparts in his consistently appealing portrayal of Johnny, an honest boy who joins the mob to pay for his mom's pancreas operation. He's a natty dresser with a heater next to his heart of gold. Nobody wipes the permanent grin off his face, not even his kid brother, the D.A., who sends him up to the Big House.

Griffin Dunne costars as Johnny's kid brother, whose early interest in Oliver Wendell Holmes coloring books presages his prosecutor's career. Piscopo plays a villainous hooligan named Vermin, in what is really an extended cameo. The excellent supporting ensemble's most prominent players are Peter Boyle, as a kind crime boss and Johnny's mentor, and Richard Dimitri, as a vaguely Italian cross-town rival named Maroni.

Maroni not only murders his rivals -- by the buildingful if possible -- he also murders the language. "You ice holds. I'm a gonna put your bells in a sleigh," he snarls. "You fargin, snealy basteeds."

Director Amy Heckerling, of "Fast Times at Ridgemont High," is an energetic, promising young director. But she's easily as smutty as "Porky's" Bob Clark. "Johnny Dangerously," sometimes brilliant, always bawdy, is weakest when she's playing macho. It's a fargin shame. JOHNNY DANGEROUSLY -- At area theaters.