It couldn't have been the first time the analogy has come to mind.

Holed up in a Toronto hotel room last week, the day before the final show on a four-stop North American jaunt, the three formerly snot-nosed punks who make up Green Day - singer/guitarist Billie Joe Armstrong, bassist Mike Dirnt and drummer Tre Cool - were trying to explain how on Earth they'd wound up writing, recording and touring American Idiot.

"Well, the Egyptians built the pyramids somehow, so we're somehow pulling this off," offered Tre, the least likely of the three to take himself seriously. "Without building Stonehenge," Dirnt interjected, prompting the drummer to break into a British accent: "Who were the druids, and what were they doing?"

That the band itself opted to invoke the spectre of Spinal Tap was a bit surprising. But anytime you start trying to follow Pete Townshend's lead with your very own rock opera - especially when it features nine-minute songs, overt political messages, lots of Roman numerals and a loose narrative constructed around someone named "Jesus of Suburbia" fighting the power in George W. Bush's America - there's a decent chance you come out looking like Nigel Tufnel instead.

But then, there's that elusive shot at greatness that makes the risk a worthy one.

"On one hand, it's like, you've got this mountain over here you've already climbed, and you know you can climb it, and the view from the top doesn't suck," Dirnt said of the usual album/single/video/tour formula that's served the band well for the past decade. "And all of a sudden you see this other mountain, and you're like, 'Gee, I wonder what's on the other side of that?’"

"I honestly don't think there would be a Green Day album out right now if we didn't go down this path," Armstrong contended. "It did get our sense of humour pumping, but it also got our creative juices going at the same time."

Then there's the lure of reasserting supremacy over the scores of Green Day imitators who've popped up since the band broke through in 1994. "If we were just going to go for the pop-punk thing, we're the best Green Day band in the world," Tre said. "So what are we going to do, rip off Green Day? Let other bands do that; we'll move on and step it up."

Remarkably, the gambit appears to have paid off. With its lead single already topping the charts, American Idiot was released last week to rave reviews. And live, as a Toronto audience found out Friday night at the final stop in this small-tour-before-the-big-tour, it's turned out to be a triumph.

Few albums can be played live from start to finish without grating on even the most faithful audience. Even if the studio version is relatively filler-free, not every track works live and the pacing is all wrong. Besides, there aren't many ticket-buyers who don't want to hear the songs that turned them onto their favourite band in the first place.

What unfolded at the Phoenix Concert Theatre on Friday, then, was a tribute both to the album and to Green Day's astonishingly polished stage act. It was, as Armstrong had predicted the day before, the sort of old-fashioned rock blowout the likes of which the audience - most of which came of age at a time when minimalist presentation ruled the day and too much ambition was widely frowned upon - had "never seen before."

There was an entrance to the soundtrack of 2001: A Space Odyssey. There were backing percussionists, saxophonists and additional guitarists. There was the band's name in lights, and a confetti-strewn finale. And through it all, there were three guys who had spent a decade smirking and sneering their way through three-minute pieces of ear candy, all playing their hearts out with hardly a hint of irony. Much as the faithful roared their approval at an encore that trotted out a few old hits and a reasonably convincing rendition of We Are the Champions, the band could've called it quits after running through the disc and everyone would have gone home happy.

When the show sagged - mostly on relatively low-key numbers like Boulevard of Broken Dreams - it quickly regained momentum with more hard-core offerings like St. Jimmy. But where it really soared was with the two nine-minute, multi-textured opuses, Jesus of Suburbia and Homecoming, and with Armstrong's wild-eyed delivery of the politically charged Holiday.

It was the diminutive singer/guitarist, in particular, who was a force to be reckoned with - a charismatic showman racing around the stage and working the assembled throng into a frenzy. "This is sort of like Billie's doctorate, you know, as far as writing songs and stuff," Tre Cool had said the day before, and Armstrong left little doubt how much he had invested in it.

Where Billie Joe and his comrades take it from here is another question. "I don't think our ambition with this album has stopped anywhere along the line," Dirnst said in response to reports of a big-screen adaptation in the works.

Let's hope it doesn't stop anytime soon, either. After years of questions about Green Day's punk-rock cred, American Idiot - a brash effort to tear down everything we thought we knew about them and the movement they spawned - is just about the punkiest thing they've ever done. And the live show it's produced looks absolutely nothing like Spinal Tap.