LOS ANGELES, California (CNN) -- Robert Plant and Alison Krauss. Once upon a time, the iconic lead singer of Led Zeppelin and the golden girl of bluegrass would never have been mentioned in the same sentence.

Alison Krauss and Robert Plant's "Raising Sand" was an unlikely collaboration that won five Grammys.

But since they won five Grammy awards -- including album of the year for their surprising collaboration, "Raising Sand" -- their names have been inextricably linked: RobertPlantandAlisonKrauss.

If they were 20 years old and ran in Hollywood circles, tabloids might be calling them Robekrauss or Aliplant.

Plant, however, is 60 -- in fantastic shape, and with a full head of the golden ringlets that became his trademark during the 1970s.

At 37, Krauss is elegant and ethereal. And while both are dead serious when talking about their craft, the rest of the time, they're like two silly junior high kids -- he, the charming prankster with a secret crush, and she, the beautiful prom queen who pretends not to be amused.

Clearly, they're both having the time of their lives, and are excited about their current musical journey -- which pushes each out of their respective comfort zones and into new territory. Now, he's a little bit country and she's a little bit rock 'n' roll.  Watch Plant and Krauss rib each other »

I compliment Krauss on her hair as a stylist touches her up. "It's not mine," she whispers.

Two feet away, Plant clears his throat loudly and points to his own golden locks. "Why, your hair looks lovely, too, Robert," I say.

"Well, you know who I am," he replies.

We are in Coldplay's vacated dressing room, two nights before Plant and Krauss swept the evening at the 51st annual Grammy Awards. This is an excerpt from our conversation in the basement of Staples Center in Los Angeles the night of their rehearsal.

CNN: First of all, this is the screwiest collaboration I had ever heard of. How did this happen?

Robert Plant: It's just sheer luck, really. I never sang with anybody before, you know -- only once ever in my life, on "Led Zep IV" with Sandy Denny [the late English folk singer, in 1971]. So this is a whole new thing. I've also been coming to the United States for 40 years -- you wouldn't believe it looking at me -- and I've never worked with Americans! This is all brand new for me.

Alison Krauss: Were we both nervous? We both were. We thought, "What are we going to do in there?" We went into the studio originally saying, "We'll give it three days and see what it's like."

Plant: Alison's reputation is 24 karat, and I'm an old rock 'n' roll singer. Even the band was kind of going, "Oh wow, how is this going to work?" It was great when we kicked in together, and I could just feel the room -- I don't want to say it, but the room lifted!

CNN: Musically, you're polar opposites. How did you blend your different perspectives?

Plant: As we got started, it was Alison's world. She knew how she wanted to proceed, and we exchanged a lot of ideas musically. And then we both agreed that because we both produced records ourselves, that we needed an intermediary to guide -- somebody to separate us, or to make the journey more clear. And Alison knew T Bone Burnett from "O Brother, Where Art Thou," and he kindly enlisted for the gig, and he brought a lot of great songs to the show.

CNN: You challenged one another to sing in different ways than you're used to.

Plant: When she goes up for these wailing notes on stage, that's where I want her to go with this new project -- occasionally visit these places where she
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