Monty Python's Spamalot, which lowers the drawbridge at the Shubert on March 17, begins - as did its source movie, "Monty Python and the Holy Grail," 30 years ago - on the promissory note of galloping madness ahead: A horseless King Arthur prances onstage, show-pony style, as his faithful manservant - the well-named Patsy - makes clippity-clop sounds on coconuts.

Silliness is, sad to say, in such short supply these days that the rebirth of Pythonic nuttiness qualifies as a genuinely blessed event. In days of yore, it was dispensed with splattering gusto by The Silly Six (Graham Chapman, John Cleese, Terry Gilliam, Eric Idle, Terry Jones and Michael Palin); now, on Broadway, it's handled by a Magnificent Seven no less adept at carrying a loony tune or two (David Hyde Pierce, Tim Curry, Hank Azaria, Christopher Sieber, Michael McGrath, Steve Rosen and Christian Borle).

All were recruited by a couple of proven comedians who know funny - director Mike Nichols and the aforementioned Idle, who has been anything but (having done the book and, with John Du Prez, music and lyrics for this broad-stroked, medieval mud-wrestle).

"It's largely Mike," Idle says of the Spamalot laughalot. "He insisted we need the very best funny people to play Pythons. I think they're funnier. I really do. I watch them and think, 'You know, they're funnier than we were with the same material.'"

Reprising historical yocks, he notes, "is not achieved accidentally. Getting Mike was a brilliant move. I had to find someone who'd take on the Python sensibility, protect it and guard it, and who had also been a great American comedian. He knows where the funny is, who's funny and who isn't and is also so wonderful no one can say no to him." Before Nichols arrived on the scene with hand-picked jesters to do his bidding, Idle relied on the laugh track in his head. It's hard to make sense of "Monty Python and the Holy Grail," let alone a musical, but he and Du Prez pressed on for three years, struggling to find some frayed thread of a narrative. The original film dispensed with trifles like a plot and an ending. It simply ended when police moved in on the Pythons and carted them off to jail in a paddy wagon; the "plot" preceding their arrest was a crazy quilt of sketches delivered in rapid-fire, scattershot fashion like bones thrown on the floor for readings.

Huge chunks of set pieces from the film have been retained and are greeted like old friends by the audience, "but the thing that gives me joy the most," admits Idle, "is that the new stuff really works. The songs work. Nobody really notices the new stuff."

What audiences will notice, though, is a Broadway necessity known as The Real Live Girl (Sara Ramirez, in a star-making turn) who mixes it up along the way with Arthur and his round-table rowdies. She delivers the period piece damsel - The Lady of the Lake (who was only alluded to in the film but here materializes with cheerleading backup called The Laker Girls). "You can't have a Broadway show with just guys running around. Funny though that is, if it's gonna be a show, you gotta get girls in. This was a deliberate attempt to create a new role. I thought, 'We've got to get a great voice to go with this,' and we definitely did."

The toughest part of the job, he confesses, was not in writing it but in getting his fellow Pythons to agree to a Grail redux. "That was the most nervous thing for me. I thought the only way to persuade them was to show them how it would be, so I spent six months doing the adaptation, then John and I did the songs. We recorded everything and sent them a CD. The song that sold them on it was called 'The Song That Goes Like This.' It just got them. It's a very Python kind of song about itself. The remarkable thing is we improvised it while we taped it. It just came out."

Yeses started rolling in within days. In fact, Cleese and Gilliam wanted to put their oars in but, then, thought better of it and let it be Idle's baby. "Otherwise, we'd never have gotten it off the ground. We could never meet. We're hopeless at meetings."

The timing is great for comedy. "What's happening now is that silliness is making its fight back. I think it's coming 'round again. When Python was first popular in this country, there was Vietnam. Well, now - hello? We're back. I think we need it again to remind ourselves how silly we are and how we're not actually all to blame for everything. We do feel somehow to blame, but we're not. We are also victims of circumstances."

It's not an accident that "Always Look on the Bright Side," the Monty Python mantra from "Life of Brian," is dropped into the new Broadway mix. "We're all children of men who gave their lives, or fought, in World War II. All the songs from World War II are cheery-uppy sorts of things. 'The Sun Will Shine Again,' 'Bluebirds Over the White Cliffs of Dover' - they're all nostalgic, wistful longings for a time of peace and happiness. The British are only happy when they're losing because that confirms their worldview."

Only one of the original Pythons made the Spamalot cut - Cleese, logically elevated from Lancelot on the screen to the voice-over of God on the stage ("Who else to play Him?" Idle wryly reasons). One day, Cleese bopped by rehearsals just as the company was breaking into "We're Knights of the Round Table," his big "Grail" ditty. "Cleesey's like me," says Idle. "We just sat there in tears because there was something so moving and wonderful and reassuring about seeing people doing this silly stuff that we wrote 30 years ago. There it is, in a different form - but still just as silly. I think, for all of us Pythons, this show is going to be very" - he waits for the right word - "heartwarming."