What happened when mega movie star Tom Cruise met mega music star Will.I.Am? The song "Someday," which the Black Eyed Peas hitmaker composed for Cruise's upcoming summer thriller, "Knight and Day." MTV News recently caught up with Cruise and Will to talk about how their collaboration came to be.

"First of all, I'm a fan of the Peas," Cruise told MTV News. "We met at a charity event and got to talking: 'We've got to find something to do together.' ... We were three-fourths of the way done [filming] 'Knight and Day,' and the Peas were playing in Miami, so we all went -- Kate [wife Katie Holmes], Cameron [Diaz] and all of us went to go see them over Super Bowl weekend. As we were watching, it occurred to me that this is the perfect time, so I called up Will, and he doesn't have any time, but I asked, 'Are you interested [in doing a song for the film]?' "

"I made time," said Will, who was then shown portions of the film to get ideas for the track. "It was easy, because the film was so good and it inspired me to write the song. When you can contribute and participate and collaborate with a film you love, that's a rare moment. That's a godsend."

Cruise was impressed with Will's ability to immediately tap into the theme of the film -- and the fact that he composed on his phone. "He wrote the song on his BlackBerry," Cruise marveled. "Right in the room."

"I don't like to let that inspiration fly away, so I jot it down in my notes," Will explained. "For 'Someday,' the lyric was 'Someday/ I don't want it to be one day, I want it right now.' So when I left the editing [room], I wanted to remember the emotion I was supposed to put into the song."

"It was very cool," Cruise said of Will's process. "[And] totally organic to the film. I think it's an incredible song."

In the film, which has been described as a "sexy action/comedy," Cruise is Agent Miller, a covert operative sent on a mission from which he was not intended to return. Diaz is June Havens, a woman caught between Cruise's agent and those he claims set him up. Through a series of double-crosses, narrow escapes and mistaken identities, they soon realize they can only count on each other.

"Knight and Day" is directed by James Mangold ("Walk the Line," "3:10 to Yuma") and also stars Peter Sarsgaard, Viola Davis, Paul Dano, Maggie Grace and Marc Blucas. The film opens June 25.

The Black Eyed Peas debuted "Someday" on Thursday at an afterparty that followed their concert at London's O2 arena. At their Friday show in London, Cruise joined the group onstage and helped them perform their chart-topping song "I Gotta Feeling."

Check out everything we've got on "Knight and Day."

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