It's Wilmer Valder-RAMA in Hollywood ... but Why?

With a name like Wilmer, it's no wonder this guy's the toast of Tinseltown.

Between his new show on MTV, his recurring role on "That '70s Show," his restaurant ventures and his laundry list of broken-hearted starlets, Wilmer Valderrama has worked his way up from sitcom obscurity to big man on the boulevard.

"Wilmer is definitely the new Ashton Kutcher," Michelle Lee, executive editor of In Touch Weekly, said of the ex of Lindsay Lohan and Mandy Moore. "There are some people who are good movie stars and good TV stars, and then there are good celebrities, and Wilmer is a good celebrity. You want to know more about his personal life. Who he's dating. Where he's partying. He's like the new Tara Reid."

But why is this not-much-better-than-average-looking, 5-foot-8, not particularly muscular minor TV star stealing the hearts of Hollywood's loveliest ladies? Not to mention that he has a weakness for kissing and telling?

Best known for his portrayal of horndog exchange student Fez on FOX's "That 70's Show," Valderrama, 26, has managed to work his character's likeability to his own personal advantage.

"Back in the first couple seasons [of "That '70s Show"] I really fell in love with his character," said Lee. "He was so naïve and so endearing, but there was also something very cute about him."

Young Hollywood also took note of the dark-haired charmer. Pop sensation Mandy Moore became Valderrama's first piece of arm candy, and a slew of "it" girls followed in her wake.

"It was kind of like a dating snowball effect. Once you date one hot Hollywood starlet, you become infinitely more desirable," said Lee.

"When he went from dating Mandy Moore to Lindsay Lohan, it became hotness by association and people were like, 'Oh my God, he's cute.'"

That said, dating Wilmer isn't all it's cracked up to be.

Lohan has blamed her train-wreck teen years partially on her heartbreaking bust-up with Valderrama, who she says was her first love.

And in a recent — and now infamous — Howard Stern interview, Valderrama claimed to have deflowered Moore and worked his mojo on Jennifer Love Hewitt, a claim the "Ghost Whisperer" actress denied.

"I was told that we had all these very steamy encounters and I was like, 'Really! Well, I would have loved to have been there,'" said Love Hewitt, whom Valderrama rated as an "eight out of 10" on the bedroom scale.

He also said the sex was "really good" with Moore, and that he's been "blessed" in the endowment department.

Such claims have led Valderrama's detractors to peg him as a womanizer, and a cunning one at that.

"He was never famous because of his acting talent, he was always famous because of who he was dating. He used those girls to get famous," said 19-year-old Wilmer watcher Danielle Stein, of Cherry Hill, N.J.

"I remember back to when he was dating Mandy Moore. The tabloids never even used his real name, they always just called him 'the guy who plays Fez.'"

Still, kissing and telling seems to have only helped Valderrama's career. In April, MTV launched the successful series "Yo Mamma," a "Yo Mamma" joke competition hosted and executively produced by Valderrama.

To date, over 60 million people have tuned in to the trash-talking contest that hands out $1,000 in "cash money" to the pithiest player — and many of them are guys.

"Our audience loves him," said MTV's Rod Aissa, senior vice president for Talent Series Development. "There is a nice 50-50 split of who watches the show. He has really helped get male teens back to MTV in the afternoon," said Aissa, who met Valderrama when he was the running gag on the first season of his pal Kutcher's prank show "Punk'd."

"During the first cycle of "Punk'd," [executive producer and host Ashton Kutcher] was always talking about how funny Wilmer was … We wanted to do something with him because he was such an accessible person," Aissa said. "Then, about a year and a half ago, Wilmer came to me and said 'Did you ever hear a 'Yo Mamma joke?'' and I said yes and he said, 'Let's do a show around that.'"

Valderrama then spent several months working out the concept and shooting the pilot, all while remaining a staple on the party scene.

"When we called him up and told him we were picking up 'Yo Mamma,' he was so blown away. You would have thought he won two Oscars. He's really such a gracious and down-to-earth guy," said Aissa.

While he couldn't be reached for an interview with FOXNews.com, approachability seems to be a key factor in Valderrama's appeal. An unpretentious dresser, Valderrama is often seen around town wearing a skull cap and jeans, which is pretty low-key for a budding movie star who also owns Dolce, one of L.A.'s most talked about restaurants.

"He is just a real guy," said Aissa. "That's why people like Mandy Moore go for him."

Fans agree: a cool personality equals big-time sex appeal.

"I don't necessarily think that he is that cute, but he seems like he has such a great personality," said 15-year-old Julia Ellner, of Woodmere, N.Y. "He just seems like he'd be really nice in real life and he's also so funny on 'That '70s Show.'"

When asked if she thought that Valderrama's star has reached its peak, Ellner quickly replied, "No way. He is definitely going to go far in his career. He's just so funny."

Lee concurs that Valderrama is sure to hit it even bigger, especially since he will be starring as Ponch in the movie remake of "CHiPs" in 2008.

However, there is something that could hold back the maturation of his career — the maturity of his girlfriends.

"[His dating habits] make me wonder what his future holds," Lee said. "He definitely has a thing for dating really young girls, and at a certain point it's going to get creepy."

"That '70s Show" airs on FOX, which is owned by the parent company of FOXNews.com.