IT SHOWS HOW important DVD sales have become to a movie's profitability that Kristen Bell ("Heroes," "Veronica Mars," the voice of "Gossip Girl") called last week to chat about "Forgetting Sarah Marshall."

Just returned to her L.A. home from a day of voter registration in Missouri, Bell cut into a rare day off, "just hanging, running errands," to talk.

On the phone, she comes across as a friendly Midwesterner (she's from just outside of Detroit) without the false front of so many actresses.

DVDs have become so important to the industry that actors actively promote them.

"It is definitely built into the shooting schedule as far as getting DVD extras," she said, "because the DVD has become such a different experience especially on [producer Judd Apatow's] movies, where you get the 'Unrated,' so we definitely do takes where you can swear as much as you want."

So it's sort of like when the porn films shoot the cable version. Except in reverse?

"Yeah, exactly."

Since comedies from the Apatow empire tend to benefit from a lot of improvisation, Bell said the "Sarah" script changed "a ton" from the time she first read it.

"I would venture to say it changed about 50 percent," she said. The plot and characters "were created by Jason [Segel] and the majority of the scenes were in there, but the way they allowed us to work - there was a long rehearsal process where we were allowed to ad-lib through all of the scenes and think up scenes on our own that would be good for characters."

And after a lot of drama, Bell enjoyed the comedy.

"It's always been my dream to become a stand-up comic," she said, "but I just don't think that I have the balls to do it. To sit down and try to write a stand-up routine would scare the bejesus out of me. I'd rather make a very long public speech. So being able to work in a comedy with all these people I admire so much and attempt to keep up with their improv skills was really thrilling."

What about writing a comedy screenplay?

"There's a sense of permanence that comes with writing," she said. "I feel like I could go into a room and, fingers-crossed, make some people laugh, have some good zingers, but to be able to put them on paper just gives me so much anxiety."

"Writers would probably say the same thing about what you do," I responded.

"I know," she said. "It's so weird the things that are in your comfort zone and being a writer is the hardest job to me. You're putting jokes on paper and 100 people are reading them and going, 'That's not funny.' That sense of judgment, I'd be crying every day. I'm sensitive."

"You seem tough in your roles."

"That's all an act."

But that sensitivity doesn't mean Bell isn't getting a charge out of her sparks-flying "Heroes" role as Elle Bishop.

"I was really pleased with what they wrote this year," she said. "It was cool to be incorporated into the previous lives of the heroes. They wrote a lot of flashbacks and it made me feel like a more important character. It was interesting how much depth they gave Elle this season and I was so grateful for it."

And your superpower?

"I'm really happy with it," she said. "If you've got a superpower you should just be grateful for it. . . . There's a sense of all-out power to Elle but also a sense of vulnerability because her power can be shut down."

"What about your sexual power in 'Sarah Marshall,' " I asked. "Did you enjoy the sex scenes? Was it embarrassing? Are you really that flexible?"

"Yes. Yes. And yes," she said.

"Wow," I said. "I should be writing this for Maxim."

"In reading a script as an actor," Bell said, "you read all these sex scenes, and I got really nervous about it, but it's not like we all don't make dirty jokes with our friends. It's not like once you've had one glass of wine you don't walk up to a chair and hump it just to make your friends laugh. The jokes about our own sexuality and horniness run rampant with people you're comfortable with, and I'd gotten so close to this crew and the other actors that by the time we shot [the sex scenes] we just had a blast. It was all for the sake of the joke."

So what was your favorite part of doing "Sarah Marshall"?

"The feeling of being accepted into [Apatow's] group," Bell said, "was so nerve-wracking but so flattering at the same time . . . and having the fun with them off-set that I did was probably the best part, because that's what gave me the courage to say, 'I can be accepted as an improv artist.' Who knows if anything I'm going to say is going to be funny but it doesn't really matter. They were really encouraging."

Is there something, I asked, to the notion that funny guys want to be better-looking and pretty girls want to be funny?

Bell laughed. "You're not going to characterize me as a pretty girl, are you?" she asked.

"You're not going to deny it, are you?" I asked back.

"I've had feedback from many an audition that would say the contrary," she said. "For the first year or two that I was in Los Angeles, every audition that I went on I was not homely enough to play the homely girl and not pretty enough to play the pretty girl.

"Everybody wants what they can't have, and being a comedian to me would be the be-all, end-all."

Not being a rock star?

"Who cares about being a rock star? Sure there's that group of semi-schlubby but adorable writer/actors that wish they were cuter but secretly they know that what gets the girl is the personality. F--- handsomeness. You can only look at someone for so long."

Anything else you'd like to say?

"Power to the people. Peace on Earth."

Anything else you'd like to say about the movie?

"I will say this," she said through laughter. "I don't know what this whole 'Unrated' thing is. I know what we shot and to me it feels like all of it was in the movie. So unless I was drunk during a scene or I wasn't aware they were filming, I'm not sure what makes this whole 'Unrated' thing. It seems like they put 'Unrated' to really tempt you, like you're buying porn or something, but I don't know what could be in there that wasn't in the movie, so I'm kind of excited to see it."

"You haven't seen it yet? Because you're out of control."

"You lie! I'm not out of control."

"People have said to me, 'I can't believe she did that.' "

"No way! . . . What did we do that could cause it to be 'Unrated'? . . . I thought that was a video camera in my hotel bathroom, but I wasn't positive . . . *