Shiri Appleby, who plays Liz on UPN's "Roswell," knows what it's like to be out of the limelight.

"I was in that position for so long," she says, "being unemployed for periods of time, just being a college student. It's fun, there's nothing wrong with that. But now, I also have to accept that people are talking to me for being on TV, not because of me, because I haven't changed."

The Los Angeles native says she was in her sophomore year at USC when she got hired to play the high-school student/waitress who falls in love with teen-age alien Max (Jason Behr), one of three human-alien hybrids (with Brendan Fehr and Katherine Heigl) stranded in Roswell, N.M.

Aired for two seasons on The WB -- and in perpetual danger of cancellation -- "Roswell" has managed to survive, if not exactly thrive. Picked up last spring by UPN, it now airs Tuesday nights at 9 p.m. ET, right after fellow WB expatriate "Buffy the Vampire Slayer."

"It's the show that doesn't want to go away," says Appleby. "It's like 'The Little Engine That Could.'"

Asked if she has a theory on why the show has endured, Appleby says, "We've been on small networks. I don't think our show would have survived on an NBC, but I also think we have a really strong fan base that doesn't want to let the show go away. The only reason we are still on the air is because of the fans."

While Appleby has yet to appear at a science-fiction convention, she has had a chance to meet her fans. "The very first season, we had a big party that all of the fans on the Internet threw, and we all went. It was great. We walked around and got to talk to everybody, meet everyone. They were really nice."

"There were people of all ages, really young kids, much older people. I think their only common thing is that they all like the show."

For the show's first two seasons, Max and Liz were the ultimate star-crossed lovers, ducking the authorities and their parents to be together, breaking up, reuniting, dealing with romantic rivals (including a now-departed fourth alien, Tess) and supernatural threats. This season, the conflicts have risen to a new level, with both lovers estranged from their parents and clinging to each other, as Max seeks mysteries from his past.

That doesn't mean it's all angst. "I don't think the show is taking itself quite so seriously," says Appleby. "It's a little more campy. Following 'Buffy,' which has that great sort of quirkiness about it, I think the writers of our show are trying to blend a little bit of that in. Humor is good, especially when you're dealing with aliens in high school."

Just because Max and Liz are ever closer, don't assume they've gone all the way. "I know she's still a virgin," says Appleby. "He's not, he slept with Tess, so Liz is the last virgin on the TV show. I was talking about it the other day in front of the writers -- time to make some changes."

Last season, Liz's best friend, Maria (Majandra Delfino), slept with her alien boyfriend Michael (Fehr); this season, Max's sister, Isabel (Heigl), is involved with human lawyer Jesse (Adam Rodriguez).

Considering that Liz has always been the show's "good girl," there might be a risk in taking her to the next level. "She's definitely young," says Appleby, "but she's gone through so much stuff, that I could see how she mentally could be ready to sleep with Max. I know there are going to be some big surprises coming in the middle of the season for her, so we'll see what happens."

So far, though, Appleby is proud that Liz has stood by her convictions. "A lot of younger girls, I feel like they look to Liz for guidance, because she's able to say no to a lot of things. That's a really uncommon thing for younger girls."

"The fact that she can take charge, stand up and voice an opinion, and not be insecure about other people's opinions, it's great. She's a fictional character that's standing up to a boy at points, and there's something to be said for that."

"That's probably one of the things I'm most proud of. When the show is finished, I'll be feeling good that that character had that stance. She doesn't like being taken advantage of."

For now, while Appleby plans to return to college one day, doing "Roswell" has given her many opportunities -- along with a best friend. "You don't mess with Majandra," she says, "on-camera or off-camera. She's probably my best friend, one of the closest friends in my life. When we're not at work, we eat a lot, we go to Color Me Mine a lot. It's where you buy these ceramic vases and paint them. We do those things. We're just very good friends."

"We've gone through such a lot, being on a TV show for three years and having it change things in your personal life. Then having one person that you don't have to explain to, because they understand the battles that you've fought at work. So there's such an understanding there."

Appleby enjoys acting, but she's not consumed by it. "The first season and a half, I'd go to Santa Barbara every weekend. I needed a break. I needed to realize that I'm still a human being, that I'm not just this piece of property, that there's so much more to life."

"Yes, it's my job. It's a wonderful job. I love my job, but I'm still a person with other thoughts and feelings."