As Mona Dearly, a screeching harridan so obnoxious that all her neighbors have reason to want her dead, Bette Midler puts on a flamboyant sneer that establishes the broadly jokey tone of ''Drowning Mona.'' But this comic variation on ''Murder on the Orient Express,'' set in an imitation Mayberry full of dull-witted Yugo drivers, isn't nearly as funny as its groovy cast -- including Neve Campbell, Danny DeVito, and Jamie Lee Curtis -- might lead you to hope.
Like ''The Impostors'' or ''Mystery Men,'' ''Drowning Mona'' is too pleased with its own outrageousness, the actors more eager to goof around in schlumpfy costumes on a low-budget lark than to play their trashy characters with the seriousness such farce requires. Curtis, as a chain-smoking waitress sleeping with both Mona's wimpy husband (William Fichtner) and boorish son (Marcus Thomas), cavorts like she's in an ''SNL'' skit. At least Nick Gomez, the indie filmmaker (''Laws of Gravity'') who's also a reliable director of big-cast TV dramas (''Homicide''), distributes the shtick equitably among this big cast. That way, no one star is more of a drowned rat than any other.