The Waterloo Bridge Theatre Company’s recently acquired performance space in Park Slope is smaller than many people’s living rooms. The stage has only a few overhead lights and does not have a curtain. Yet it is in this tiny theater that some of the liveliest and most innovative Shakespeare you have ever seen is being performed.

The company’s current production, "Twelfth Night," is directed by Michael Hagins, who also stepped into the role of Sir Toby Belch after the actor who was originally cast suffered an injury. It features a troupe that is superb down to the most minor roles.

Written in 1600, when Shakespeare was 36 and leaving his youth behind, "Twelfth Night" stands on the optimistic belief that love conquers and cures all, and is tempered by the sure knowledge that lovers are often foolish and fickle and life is frequently unpredictable. The play is based on an old, Italian comedy, "Gl’Ingannati" (1537), which Shakespeare had already used for "Two Gentlemen of Verona." Like most of Shakespeare’s comedies, its central conflict involves disguises and mistaken identity and is resolved by suitable marriages.

In "Twelfth Night," Sebastian and his twin sister Viola are shipwrecked off the coast of Illyria, each believing the other has perished. After Viola is rescued by a sea captain, she disguises herself as a boy, Cesario, and becomes the page of Orsino, duke of Illyria.

As Orsino’s page, Cesario is sent to the home of the rich countess Olivia, who is in a seven-year mourning period for her dead brother. There he is to advance the suit of the lovesick duke. Olivia doesn’t budge in regards to the duke but falls instantly in love with Cesario.

The play also has one of Shakespeare’s most amusing subplots: the clever scheming of Olivia’s drunken uncle Sir Toby Belch; Sir Andrew Aguecheek, a knight he has introduced into Olivia’s household in the hope he may win her hand; and Olivia’s waiting woman, Maria - all of who want to get even with Olivia’s steward, whose name, Malvolio, meaning "ill will," explains their attitude.

Presiding over this messy situation is Olivia’s clown, Feste, the fool whose profound wisdom is probably Shakespeare’s own.

Hagins has made only two noteworthy changes to Shakespeare’s script. He has turned Malvolio into a Mafioso-type bodyguard (the fantastic Bruno Campolo) dressed in a black suit and toting an impressive hand gun.

And Antonio, the sea captain who rescues Sebastian, has become Antonia, whom Elizabeth Vocam creates as a feisty, irrepressible young lady madly in love with the man she saves from the sea. These changes work so well and seem so fitting, it almost seems that Shakespeare should have considered them himself.

Given the almost bare set (limited to two square boxes that serve as stools), minimum costuming (Sebastian and Viola - as Cesario - wear jumpsuits and the clown wears a jester’s cap) and the intimacy of the theater, the audience cannot help but concentrate on the actors’ delivery of the Bard’s magnificent lines and the physicality of the actions that accompany them.

Of the principals, Robyn Berg’s Olivia is passionate and hilariously extravagant in stark contrast to the decided composure of Julie Ann McMillan’s Viola/Cesario. Colin Pritchard creates a sufficiently smug and self-centered Orsino, but could have come in a little heavier on the lovesick sighs that accompany lines like, "If music be the food of love, play on."

Likewise, neither Hagins nor Patrick Egan, as Sir Andrew Aguecheek, made their characters outrageous enough to bring out all the humor inherent in those roles. Sir Toby Belch stands next to Falstaff as one of Shakespeare’s bawdiest, and at the same time wisest, clowns. And his sidekick, the worthy knight, is certainly one of Shakespeare’s biggest jerks. When playing either of these individuals, it’s almost impossible to overact.

Having mentioned these minor failings, it is important to emphasize that frequently this production relies on supporting characters as a major source of laughter. Elizabeth Munn as Maria, woman to Olivia; Caroline Price as Fabian, servant to Olivia; and Rick Redondo as Feste (who also sings and plays the guitar beautifully) all make major contributions to the fast pace and high pitch of the production.

Like many people over a certain age, this reviewer has seen "Twelfth Night" more times than she would care to count. Nevertheless, the Waterloo Bridge Theatre Company has brought an excitement and originality to this play that makes it fresh and new once again. For all those fearful of braving the cold to get to this somewhat out-of-the-way playhouse, remember: there’s nothing like laughter to keep you warm.

The Waterloo Bridge Theatre Company’s production of "Twelfth Night" plays through Feb. 8, Thursdays through Saturdays at 8 pm, and Sundays at 3 pm. Tickets are $15, $10 students. The Waterloo Bridge Playhouse is located at 475 Third Ave. at 10th Street in Gowanus. For reservations, call (212) 502-0796.