David Boreanaz

You can wish David Boreanaz "Happy Birthday" today (he turns 37), but don't even think of throwing him a surprise party. That's because, despite taking center stage in the crime drama Bones (whose season finale is Wednesday), he'd rather not be the center of attention off-screen. Boreanaz, once TV's sexiest bloodsucker on Buffy, the Vampire Slayer and Angel and now FBI agent Seeley Booth on his FOX show, is a lot more comfortable playing dad to 4-year-old son Jaden (with actress and former Playboy model wife Jaime Bergman). PEOPLE.com caught up with Boreanaz about his favorite part of being a parent and why he's put his vampire days behind him.

Bones has been renewed for another season. You must be excited.
I'm just excited that I got through a year. I love (my character) Booth, I love the people, I love the environment. I'm a little wiser than I was when I first started out doing this. I've still got a lot to learn – I've only been in this business nine years as a working actor.

Have you done any FBI training for this role?
I worked with Mike Grasso, who's a technical adviser in L.A. I worked some handguns and some psychology training – just how you question people in interrogation rooms, little tactics that he uses.

I've heard that you're a prankster on the set.
I don't want to get into that (laughs). Whatever the moment spurs on for me, I'm gonna do.

How has fatherhood changed you?
It's given me a clear understanding of priorities and responsibilities – things aren't just all about you. It was really easy when I had no responsibilities.

What's the best part of being a dad?
To see him come in after a long day and share his experiences with me and having him run to me like he's about to do right now. He's got this big smile on his face, he's chomping some gum. Being a dad for me is about this right here.

You're celebrating your 37th birthday. Any fun plans?
I'll be working. Last year, my wife threw a surprise party for me. I get very nervous at surprise parties – I don't do well with surprise parties.

Why?
Everyone's laughing and all of a sudden all of that energy is on you.

As an actor, I would think you wouldn't mind that.
I'm really weird like that – I enjoy the craft and the work, but I get nervous with interviews and stuff like that. If I do a talk show, I'll know it'll go well if I'm chewing gum and then I spit it out at the last minute. These quirks get me through things.

You must still get a lot of fan mail and people coming up to you on the street to talk about Angel and Buffy.
I don't know, it's all different every day. I'm eluding a lot of stuff, aren't I?

Is this something you don't like to talk about?
I've never been to my class reunion – some people like to do that, I don't. I don't like to relive the past. For me to do that, I have to sit down and have a cocktail. And I can't do that now because I've got to go work out.

Source: PEOPLE