Lex Luthor: heartthrob? Michael Rosenbaum, who plays Superman's future nemesis on the WB's Smallville, has made the supervillain-to-be so appealing that fans dubbed him "Sexy Lexy." But on the Dec. 8 episode, Lex reaches a major crossroads. "A lot of people I bump into say, 'We don't want you to turn evil!' " Rosenbaum says. "But they know he's been fighting this for a long time." The actor, 33, talked to PEOPLE.com about his latest test of character and got personal – about his eccentric family, the perfect date and more.

It's Smallville's fifth season. Are you looking forward to finally playing an evil Lex?
This has been a whole journey of Lex becoming the ultimate villain in comic-book history: His mother dies, his brother Julian dies and he's got this evil dad. To watch him grow up trying to do the right thing all the time, it's like, "He deserves to kick some ass right now!" There's nothing like telling someone off or having someone killed. On the show, of course.

What else is in store for Lex?
The Lex and Lana relationship is going to really heat up. They're both kind of lonely, dark creatures, and I think there's some attraction there. And obviously the relationship between Clark and Lex is probably going to get worse. It's sad, because I think Lex really likes Clark. He's a nice kid, but he doesn't trust me. Why wouldn’t you trust Lex Luthor?

What's it like maintaining a bald head?
I get a straight razor to my head every day, and I've been doing it for five years. I once figured out I'd shaved my head like 600 times. I'm butt-cheek soft, usually, and thank the Lord almighty, it's still growing.

What's the secret to staying butt-cheek smooth?
Kiehl's cream on the head, and Kiehl's Blue Astringent after shaving. You've gotta sprinkle that on, close the pores, kill the bacteria. You've gotta spring-clean.

Tell me about Welcome to Paradise, the show based on your adolescence that you're writing for FOX.
I was such a little nerd. I was the smallest kid in my entire high school. We moved (from Long Island, N.Y.) to Newburgh, Ind., in 1980, and I had this wacky, crazy family. What's funny is the situations that this (character) is put through.

For example?
My mom once wrote me a check for 85 cents, for lunch. Do you know how embarrassing that is?

So is there a Mrs. Lex Luthor these days?
You know, there's not. It's just not easy, going back and forth between L.A. and Vancouver (where Smallville is filmed"). It'd be nice, I'd like to meet someone. I'm getting the heat from my grandparents. They're like, "Mike, come on, when do we get great-grandkids?" Every time I meet somebody: "She sounds great!" To them, if she's breathing, she sounds great.

What do you look for in a girl?
Someone who can put up with me. I'm not easy. I admit it though. Don't think you're dating Mr. Cool, 'cause I'm anything but Mr. Cool.

How so?
I mean, I've got action figures hanging up in my house. Behind me is an autographed Napoleon Dynamite poster. I have a karaoke machine downstairs, I have a conversion van – I'm a 33-year-old, some people would call it loser, but I have fun.

What's your idea of a perfect date?
The perfect date would probably be going to Disney World and riding Space Mountain and the Aerosmith ride and the Twilight Zone ride until you're about to hurl. Then you'd probably go to Epcot, where you can go to, like, 10 different cities in the world! How many girls can say, "I went to Italy, Spain, Mexico, London – all on one date!"