Unwashed, unkempt – that’s Ashlee in ‘Undiscovered’

Playing an aspiring singer and actress trying to make it in Hollywood shouldn’t have been much of a challenge for Ashlee Simpson.

But for her first major big-screen role, in the new “Undiscovered,” the “7th Heaven” TV veteran went Method.

“I felt like the character really didn’t care about her appearance and how she looked and whatnot, and I really wanted to feel that way,” Simpson says, explaining why she would often go a week at a time without showering.

“I’m so glad that I’m just now learning this,” quips co-star Kip Pardue. “I mean, we wouldn’t have talked.”

With the new movie and a new album set to drop in October, Simpson is back on the bathing train. She’s also gone blonde again, after sporting raven tresses around the time of filming.

While Simpson’s character, Clea, is probably only the fourth or fifth most important in the “Undiscovered” ensemble, Lions Gate is emphasizing the rising star’s presence. It’s a promotional strategy that probably goes somewhat against Simpson’s desire for the small film.

“I was looking for a movie where I wasn’t the lead in it and a movie where I could go in and work with great actors,” explains Simpson, probably as well known for her MTV reality show and oft-mocked “Saturday Night Live” meltdown as for her artistic endeavors. “I didn’t want to have to carry my first movie.”

Some of Simpson’s co-stars admit that they were initially wary that she might be a distraction on set.

“What do you expect from someone who’s 19 and is a multimillion dollar superstar?” says one, Pell James. “I was really nervous, like, ‘Oh God, what’s it gonna be like?’ “

But as it turned out, James says, “She was so nice. She knew all her lines. She came in. She did it.”

James was particularly impressed with Simpson’s frantic schedule.

“She’s like this little machine of work,” she gushes. “After work she would go and record albums and then fly away for the weekend to do concerts or wave in a parade one time. Seriously, she has this crazy 24-7 work life, and it’s really impressive.”

Simpson, whose sister Jessica spent her late summer promoting a hit movie (“The Dukes of Hazzard”), enjoyed the busy schedule, using the different working paces to recharge.

“For me, playing shows is so much fun, so it was nice to go back and forth and have both of them,” she says. “Maybe I just get energy because I’m 20. It might all go down soon.”

With a full autumn looming, Simpson seems poised to take advantage of that energy while she’s got it.

“I think right now I’m going to focus on my record coming out and hopefully after I go on tour, I’ll come back and be able to do a new film,” she says. “Character-wise, I would love to do something like a ‘True Romance’ or ‘La Femme Nikita.’ “

Who knows what kind of Method tricks Simpson would have to perform to get into that kind of character.

The birthday bunch

Actor-director Richard Attenborough is 82. Actor Elliott Gould is 67. Movie director William Friedkin is 66. TV personality Robin Leach (“Lifestyles of the Rich and Famous”) is 64. Singer Michael Jackson is 47. Actress Rebecca DeMornay is 43. Actress Carla Gugino is 34. Actor John Hensley (“Nip/Tuck”) is 28.