Fluffy, frothy 'Razzle'; '42nd Street' dazzles; 'Within' needs elbow room; 'Nightclub Cantata' merely survives; Stoppard 'out for a fling'

Boston seems happy to take Tom Stoppard any way it can get him - if not in the original, then as translation. So even an adaptation of a 19th-century Austrian farce, when penned by the inimitable author of ''The Real Thing,'' is bound to satisfy.

Stoppard's ''On the Razzle'' - a reworking of ''He's Out for a Fling,'' by Johann Nestroy - is a cream puff of a play: all fluff and froth with nothing weightier than plot machinations and linguistic stunts to hold it down. It is also Stoppard at his most playful - verbal feints and fastballscq - but with no philosophic core.

For the audience there is nothing more important to do than settle back and watch the cartoony scenery zoom by and catch all the jokes - double-entendres, puns, and bons mots fresh from the playwright's bag of verbal tricks. Stoppard is clearly enjoying himself when he tries to milk the most laughter from confusing ''niece'' and ''knees'' and such lines as ''mounds of figs and pyramids of uncertain dates.''

Nestroy's work - which also formed the basis of both Thornton Wilder's ''The Merchant of Yonkers'' and ''The Matchmaker'' (which later became ''Hello, Dolly!'') - details the roguish adventures of a prosperous proprietor of a provincial provisioning shop and his two assistants gone AWOL in nearby Vienna. Stoppard's adaptation, which originally opened in London in 1981, is truest to the original. Stoppard has simplified the plot, created new dialogue, retained the individuality of characters, and followed the traditional commedia dell'arte structure: two plot lines, one detailing the highborn, one the lowborn.

Under the skillful direction of Thomas Gruenwald, ''On the Razzle'' more or less rollicks along to Stoppard's beat. With scenery that looks like a pop-up greeting card, zippy offstage organ music that mimics that of a game show, ''On the Razzle'' is a concoction for eyes and ears. In a relatively solid cast, Gary Beach (as Weinberl) and Susan Pellegrino (as Christopher) were clear standouts. While occasionally the actors swallowed their lines, thus rendering some of the jokes inaudible, the star of the show - Stoppard - was clearly heard. ''On the Razzle'' plays at the Huntington Theatre through June 3. WS