WILD OATS -- At the Folger through January 20.

John O'Keeffe is not to be mistaken for William Shakespeare, even if he used a lot of the same lines and is now performed by Shakespearean companies.

The Royal Shakespeare Company plucked his 1791 comedy, "Wild Oats," from wherever old theatrical smashes go when their time has passed, and made it a modern hit in London; and the Folger Theater Group has opened an equally delightful production here. "Wild Oats, or , The Strolling Gentleman" is wonderfully silly, with clever lines and frantic stage business, and a plot so frankly dumb that you have to love it. Folger goes all out, with a real rainfall on stage, and the wealth of small, perfect characterizations for which the company is known.

But let us not, in the current spirit of indiscriminate historic preservation, revive the other 70-some forgotten farces that O'Keeffe wrote when blindess put an end to his acting career. In the great period of the Restoration stage, he seems to have filled the modest but useful position of writer of reliably funny if conventional plays, untouched with the comic genius of Sheridan, for instance, but enjoyable and playable. The Neil Simon of his day. His day seems suddenly fresh to us, but a large dose of mistaken identities and long-lost heirs would soon cure that.

In the meantime, there isn't a better giggle around. Under Leonard Peters' direction, the roomping is inspired. The stock characters are acted with such engaging enthusiasm that they become as lovable as indiviudals. John Neville-Andrews plays the lead, a traveling actor with "the abominable habit of quotation," as his best friend remarks, with a top-notch double-take expression. And the older generation of characters -- two fathers, a mother and a sidekick -- are particularly bursting with comic vitality, in the persons of Ralph Cosham, Moultrie Patton, Mikel Lambert and Richard Mathews.

The Folger company, justly acclaimed for its ability to do our heritage's most complex plays, ought to get full credit here for the quite different achievement of having plumped out a thin one.