Just ask Clay Aiken (Spamalot) or Diana DeGarmo (Hairspray).

Still, it's a little shocking that the production of Ain't Misbehavin' taking over the Academy of Music this weekend for five shows is stocked with no fewer than three Idol singers.

Even more unusual: All three - Ruben Studdard, Frenchie Davis and Trenyce Cobbins - emerged from the same Idol crop, the hit show's second season in 2003.

What are the chances of their being reunited for the national tour marking the 30th anniversary of this Tony-winning revue?

Pretty slim, according to Cobbins.

"I know they wanted Ruben," she said from her cell this week during an eight-hour bus ride from Sarasota, Fla., to Roanoke, Va. "They built the entire show around him." (It's directed by Richard Maltby Jr., who helmed the original production.)

Davis was something of a shoo-in after spending four years in the Broadway cast of Rent.

Cobbins was the long shot.

"I did not make it to the New York audition," she said. "I ended up having to tape it. The producer said it sat on his desk for days while he auditioned other people. And when he saw it, he said, 'Oh my God, she's perfect for the role.'

"I was like, 'Wow, it must have been meant for all three of us to be together again.' "

The energetic show is built around the music of Thomas Wright "Fats" Waller, the Harlem pianist who became a prolific hitmaker and recording artist in the 1930s.

The period music isn't that great a stretch for these Idolators.

"In middle school, my band teacher introduced me to jazz and I really got into it for a while," Studdard said the following day as the convoy motored on to Charleston, W.Va. "Between 10 and 13 I wasn't into popular music. I was into classical and jazz. And Fats Waller was one of the composers I really liked.

"I never thought in a million years I would be doing a play based on his music," he continued with a laugh. "And the original star of Ain't Misbehavin', Nell Carter, is from my own hometown" of Birmingham, Ala.

As Studdard learned about Waller's brief life (1904-43), he came to admire more than the man's talent.

"I'm amazed at the things he was able to accomplish, because those were hard times, especially for African American musicians," Studdard said.

"A lot of the things that Fats Waller is famous for, he probably made $80 on. . . . It's amazing he was able to keep a smile on his face. I don't imagine I would be able to."

For Davis, it's the second time around in Ain't Misbehavin'. "I did this show my second year of college" at Howard University, she said. "My professor," David Alan Bunn, "is the conductor and piano player for this production," and was the musical director when she did it in college.

The material remains challenging. "1930s jazz is not easy music to sing anyway," Davis said. "But when you have to sing it in five-part harmony, that's where all the hard work comes in." (The cast of the touring show is rounded out by David Jennings and Patrice Covington.)

Any time you stage a class reunion, attitudes about the old alma mater tend to differ.

As the winner that season (over Aiken), Studdard, 30, got the biggest boost from the show and remains a fan.

"Each year they find another crop of talent that's completely different," he said. "There's always a surprise. To me, David Archuleta," last season's runner-up, "was a huge surprise."

Cobbins, 28, finished fifth, but remains convinced the deck was stacked against her. "I don't think Simon [Cowell] ever wanted to give me my due," she said. "I think he wanted it to come down to Ruben and Clay. That was in his mind from Day 1."

Davis, 29, gained an enormous amount of early attention but was summarily dismissed when it was discovered she had posed topless as a teen. To this day, she bridles at even being associated with the show.

"Four years on Rent and five minutes on Idol," she said huffily. "I think Broadway wins that competition."

All are adjusting to the rigors of a seven-month stage tour.

"Doing eight shows a week - I've never experienced that before," Studdard said. "You have to make sure you're taking your vitamins and eating right."

Cobbins is looking forward to three nights in Philadelphia after a string of one-night stands.

"The disadvantage of going city to city is that by the time you get there and get off the bus," she said, "you go right into a performance. You have to exude more energy because you're a little lethargic."

"The whole cast has been catching each other's colds," Davis said. "It's my turn. I caught the stage manager's cold. Ruben started it. He got sick first and now it's all over the place."

The bug moves faster on the ladies' bus because they travel with the band and crew. As the main attraction, Studdard is afforded the luxury of his own bus.

Said Cobbins, "I keep telling Ruben, 'One of these days I'm going to sneak on your bus. And there's nothing you can do about it.' "

Hey, it's a long tour, kids. Let's not start misbehavin' now.