PEOPLE always expect Ben Stiller to be funny.

It's not surprising, given that he's made a career out of a string of hilarious characters; from the over-the-top vanity of male model Derek in Zoolander to his recent turn as an actor desperate to be taken seriously in Tropic Thunder.

As one of the most successful and esteemed comic actors in Hollywood, he isn't always able to hide his star power - even in the most unusual situations.

"I've had somebody ask for an autograph at a funeral," he admits, wryly.

"That might not be appropriate. I gave it to them. I don't want to lose a fan. It was a family person who was closer to the deceased than I was, so I didn't want to rain on their parade even more.

"There is some expectation, I guess, to always be funny, but it's more how you take it in yourself, like whether you care about that or not," he adds.

"You go on a talk show and people want to laugh. They want to see the funny guy be funny. But in life, I don't see feel any sort of pressure to have to do that. Because it's just too much pressure. When you're living your life you want to relax a little bit. Enjoy the funeral - you know what I mean?"

Ben has plenty of reasons to enjoy life as he approaches his 43rd birthday.

Tropic Thunder, which he co-wrote and directed, did brisk business at the US box office, knocking the phenomenally successful Batman film The Dark Knight off the top spot. And his latest movie, Madagascar: Escape 2 Africa, the sequel to the 2005 hit animated film, in which he voices Alex the lion, also made No. 1 in the American movie charts.

"It wasn't hard to decide to do the sequel because the first one was so much fun," Ben says.

"So with the second one, once you've done it and you understand what the process is, it actually makes it a bit more fun because you understand that there's actually going to be a movie at the end of it. The first time we always wondered if they were making a movie because it went on for so long and we didn't see anything."

Animated films of this calibre take years to make, and can be a tricky task for actors.

The stars usually have to voice their parts alone in a studio vocal booth, which was the case for Ben's co-stars David Schwimmer (Melman), Jada Pinkett Smith (Gloria) and (Moto Moto).

Ben was lucky enough to be paired up with Chris Rock (Marty) for many of his scenes.

"It's a strange process because you're alone in the room a lot of the time," he admits.

"Sometimes there's another actor there. If it's not Chris, there's somebody else there to read the lines with you. And that's really helpful. It's always funny to see the guy they get to read Chris's lines. They're nothing like him. And I find humour in that. It makes me laugh which is good for the energy."

Since voicing the first Madagascar movie, Ben has become a dad to Ella, five, and Quinlan, three, with wife Christine Taylor. He admits that fatherhood has made him more open to choosing family-friendly roles.

"You're aware of it when you have kids," he says.

"You just become aware of movies that you can watch with your kids and if you have the option to do some then that's a good thing, I think that's probably why I did Night At The Museum in the first place and this one too. My kids enjoy Alex and they like Marty. They're big penguin fans. They enjoy the whole thing."

In fact, Quinlan and Ella got more involved in Escape 2 Africa than just being fans. They came into the studio to help provide the voice of the 'young Alex', ending up supplying around 45 seconds of air time - apparently the kids weren't that keen on being confined to the vocal booth.

But despite this brief taste of stardom for his kids, Ben isn't interested in becoming a pushy Hollywood dad.

"I would never force them to do anything they didn't want to do, in terms of that," he says.

"I don't understand how kids who do it at such a young age can get out there and ever really want anything.

"I would keep them out of the acting arena until they're old enough to have had a little bit more life experience. I think for fun, like in school plays or just in camp-type things, nothing professional, would be my hope for them. It's every parents' choice really.

"I know, having grown up around it, I would like them to not have the pressure of having to audition for something, the rejection of that and all that stuff. It would be good not to have to deal with all that at a young age."

Being an in-demand actor, director and writer does mean time is a precious commodity for the star, who lives in Los Angeles with his wife, kids and their three dogs. He watches most of his television on digital recorder TiVo - favourite shows are 24 and news programmes - and he admits his music taste hovers somewhere in the 1990s.

He is cagey about his next directing gig, after the success of Thunder which he is "very proud of", maintaining he is in the directing business for creative reasons rather than for making big box office bucks.

"You're aware of the box office but you can't focus on it too much because you can't base everything on it in terms of whether or not you feel good about something," he says.

"That's not a fun way to live your life."

But whether Ben continues to just star in comedies or turn, like Robin Williams or Jim Carrey, to more dramatic roles, people will always expect him to provide the laughs.

"It's important to do whatever interests you and I've always been interested in different kinds of things," he says.

"It just depends on which projects are at what stage when you make them, what's ready to go. It's great to be able to go in and out of different kinds of things because it keeps it interesting. But in terms of comedy and getting burned out, I think you really have to keep yourself interested and vital."