Director Mike Leigh has usurped his subjects' mirthful sense of humor and penchant for prolonged presentation in his new film "Topsy-Turvy," a jaunty, jolly, light-hearted look at the lives of Victorian operetta architects Gilbert and Sullivan.

Like G&S, Leigh delights in garnishments that add color to his characters and to the pliant performances such details inspire.

Leigh's actors are always especially absorbed in their parts because of the way he works -- creating the screenplay in concert with his players during incessant rehearsals -- but in contrast to his downcast-but-hopeful, slice-of-life dramas ("Secrets and Lies," "Career Girls"), this picture radiates a distinct playfulness that is nothing short of contagious.

The film drops us right into a rift that formed between the duo in the wake of their biggest flop, "Princess Ida" (the movie's title comes from a London Times review that called Gilbert the "king of topsy-turvydom").

A bedridden Arthur Sullivan (Allan Corduner) -- the composer -- perhaps contemplating mortality and considering his legacy, wants to abandon their collaborations of famously light fare in favor of dedicating himself to serious opera. "I cannot waste any more time on these simple soufflés," be bemoans like a peevish child with lamb chop sideburns.

For his part, the insulted William Schwenck Gilbert (Jim Broadbent) -- the playwright and a perfectly proper, pompous sourpuss -- is beside himself, as he always considered that he was the one sacrificing his words to suit Sullivan's music. He honesty doesn't see the irony when his partner points out most of his plots turn on "a magic coin, a magic lozenge and now a magic potion."

But after sulking around for several months, Gilbert find himself reinvigorated by an afternoon at a Japanese cultural exhibition in London, and after talking Sullivan into one more go at it, "The Mikado" is born.

The machinations of staging this now-classic -- if innocuous -- humorously imperial homage to Asian culture are the at the axis of "Topsy-Turvy's" very English farce. Around the preparations turn the undiminished lives, personal and professional, of its creators: Their highs, their lows, their quirks, their divergent personalities and their rivalry.

Both Broadbent ("Little Voice") and Corduner ("The Impostors") give illustrious performances that deftly walk a comedic-dramatic line, and almost every scene is a pleasure, thanks in part to Leigh's obvious devotion to the material (the film is very well-researched), his meticulous dedication to detail (there's this one great cut-away to a chorus girl, backstage, ambitiously mouthing the lead's lines) and his wonderfully droll period dialogue. Favorite line, mostly because of harumph-ing Broadbent's sanctimonious delivery: Gilbert describes his mother as "the vicious woman who bore me into this ridiculous world. No one respects her more than I do, and I can't stand the woman!"

Leigh's catching comical bent extends even to making sport of the technological advancements of the day -- characters coo over new-fangled reservoir pens and shout into rudimentary telephones.

But he saves plenty of time for staging entire sections of the play as well, both in rehearsal and in performance (you walk away humming the vacuous and maddeningly catchy "Three Little Maids From School") -- and also for secondary stories involving G&S's favorite players, including coddled Robert Temple (Timothy Spall, "Secrets and Lies"), prima donna Durward Lely (Kevin McKidd), lonely romantic Leonora Braham (Shirley Henderson) and coquettish Jessie Bond (Dorothy Atkinson).

It hardly needs mentioning in a Mike Leigh movie, but the acting of all of the above approaches poetry in their syncronicity with the material.

The movie is lengthy, and Leigh meditates on trivialities, but engrosses you in the vivid details of this fascinating duo.

"Topsy-Turvy" will likely not draw an audience much outside the Gilbert and Sullivan Society circles, but anyone else who happens upon it will doubtless enjoy themselves -- even if they don't really know what they're watching.