Credit: Rick Rowell/Getty Photo: Nathan Fillion and His Girlfriend Arrive at The 2010 American Music Awards
When our favorite (read: hottest) TV stars fall in love, we feel one of two things: a) excitement for their happiness or b) excitement for their happiness, mixed with a good ole’ heap of jealousy.

The latter is how we feel whenever we read about sex pot Nathan Fillion and his latest main squeeze, Kate Luyben. If you’re thinking, “Um, who is that?” — don’t worry, we did, too. Kate is actually an actress — a C-list one, perhaps, but an actress nonetheless — who has appeared on True Blood and The 40-Year-Old-Virgin (as, um, “Girl With Videotapes”).

We wouldn’t really expect Nathan to go after the typical tan, bleach blonde type, but maybe that’s just ‘cause he looks so cute next to brunette beauty Stana Katic (Beckett) on Castle. But regardless of his gf’s (lack of) celeb status and the scalp-damaging dye job, we gotta say, she’s pretty cute.

Nathan is reportedly very happy with his tow-headed sweetie, too. She’s been photographed by his side at several recent events, including The American Music Awards and the Castle Season 3 premiere. “He’s always happy to show Kate off,” an insider dishes in the December 13 issue of Star. “She might be a keeper.”

So what’s her secret? How did Kate win Nathan’s heart? She gives him ample space for his fave pastimes, like playing video games and hanging out in his “man cave” (yes, that’s what he calls it). “He’s cute and charming, but very boyish,” says the insider. “Kate lets Nathan be himself.” Sounds like a pretty healthy relationship to us.

But hey Nathan, if you ever get bored, we’ll let you play our Wii anytime.

Source: Celebitchy