"Fame comes and goes, stars rise and fall, but dreams live forever."

So goes the tagline for "Dreamgirls," the upcoming film adaptation of the hit Broadway musical that scored eight Tony Awards in 1981 and later triggered a dream for Beyoncé Knowles: a starring role the budding actress could really sink her teeth into.

"Oh God, I just light up when I [talk about that movie] because I wanted it so bad," Beyoncé gushed while promoting her stint in "The Pink Panther," out Friday (see "Beyonce To Star Opposite Steve Martin In 'Pink Panther' "). "I'm doing it for real this time. I never wanted anything as much as I wanted that [part]. Finally, I'm able to play a character with range."

Knowles is deep into production in Los Angeles for the film, which revolves around the rise of the Dreams, a group of three promising female singers who break down racial barriers in the music business in the 1960s (see "Beyonce In Talks For Potential 'Dream' Film Role"). The story is loosely based on the story of Diana Ross and the Supremes, with Beyoncé starring as the Dreams' lead singer, Deena Jones. Former "American Idol" finalist Jennifer Hudson and Tony Award-winning actress Anika Noni Rose round out the group, playing Effie Melody White and Lorrell Robinson, respectively. Oscar-winner Jamie Foxx is the Dreams' manager Curtis Taylor Jr., who offers the girls a chance to become the backup singers for James "Thunder" Early (Eddie Murphy), managed by Marty Madison (Danny Glover).

"I know I'm supposed to be Deena and I know I'll do a great job at it. I'm very confident in that. I've been [a fan] of 'Dreamgirls' since I was 15. I know every little detail about her," insisted Knowles.

The singer is even slimming down a bit for the role. "I want to look different than myself," she explained.

Foxx says people will be amazed by the singer's transformation into Deena. "Obviously Beyoncé is one of the most gifted singers in the world, and now you get a chance to really see her act and put the whole package together," he said.

Although Beyoncé had notable roles in "Austin Powers in Goldmember" and "The Fighting Temptations," she feels she has yet to really challenge herself as an actor.

"I don't think people have any idea what I can do as an actor," she said. "Even though I do play a singer, there are some very dramatic and emotional scenes that have nothing to do with music. Deena starts off 16, with no makeup, bushy eyebrows and the crazy wig, but then she grows up and [blossoms] into a real diva."

While Deena's life parallels Beyoncé's own pretty closely — both started out in a girl group before branching out into other projects — the Destiny's Child singer admits she really had to work to convince director Bill Condon to consider her for the role.

"I really had to prove myself, but after they saw it, they were like, 'OK, she is Deena,' " recalled Beyoncé, who looked to veteran performers like Ross and Barbra Streisand for inspiration.

Knowles is putting any music plans on hold for the moment as she devotes six months solely to the film, which she hopes will cement her status as a bona fide movie star.

"It's just been a dream, literally. I'm learning so much every day and I'm even shocking myself at some of the things I'm doing," she said. "I'm completely becoming Deena."

"Dreamgirls" is slated for a December 22 release.

Check out everything we've got on "Dreamgirls."

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