Neil Patrick Harris is 26.

But the baby-faced Doogie Howser, M.D. star still looks like he gets carded at clubs.

What's his secret?

"I take these little blue pills,'' he says, laughing. "No, it's a lot of lotion. When I was younger, people would always say to me, `Be happy because when you're older, you'll look younger.' ''

Harris has a lot to be happy about. He's starring in Stark Raving Mad, a promising new NBC sitcom in which he plays a neurotic book editor forced to work with an unorthodox horror writer.

While the odd-couple show is already being compared to, well, The Odd Couple, Harris says he watched a year's worth of Will & Grace to prepare for the role. "It's a great show, and it's a little over the top and that was good for me to watch to see how full-bodied my acting needed to be," says Harris.

Acting is something Harris always wanted to do. The New Mexico native capitalized on the break he received at 14 (he met a screenwriter at a summer drama camp) by landing the role of a young boy troubled by his parent's divorce in Clara's Heart, starring Whoopi Goldberg. After appearing in an episode of Burt Reynolds' B. L. Stryker in 1989, Steven Bochco tapped Harris to star in Doogie Howser as a precocious teen doctor coping with normal teen problems. Harris showed both his comic and dramatic range on the ABC show, which was canceled in 1992.

"I'm really proud of that show and being known as that character," says Harris. "It wasn't like it was Family Matters. It was a well- written Steven Bochco show."

But it's a character Harris would like to put behind him. After Doogie got canned, Harris chose not to work in TV for several years. "It was important to have a respite from being seen in TV before I was seen again," he says. "It's detrimental to jump from one show to the next because then you're known as being a TV actor. I was going through so many physical changes, I just wanted to grow up a little bit."

None of that growing up, however, included college. Does Harris miss having that kind of experience?

"A little bit, but I got such a great education on the series," he says. "But I missed a little of that social culture, that feeling of being anonymous and just cavorting around in a drunken stupor from bar to bar when you're a freshman."

In the past few years, Harris has certainly been keeping busy. He appeared in Starship Troopers and played a cunning, back-stabbing king in the CBS miniseries Joan of Arc. Two years ago, he made his musical debut in L.A.'s production of Rent, playing Mark, the aspiring filmmaker. "I listened to that music in my car for about a year before I got the part," he says. "But people were disappointed I was in it. They were like, `TV people in Rent? Is that what it should be?' ''

His other stage credits include starring roles in Romeo and Juliet, Luck, Pluck & Virtue and A Fair Country. In fact, Harris says he' d like to direct theater one day. "I've always seen things from the big picture, instead of that tunnel-vision focus actors tend to have, " he says. "I like to be in charge of everything."

Harris co-stars with Madonna and Rupert Everett in the feature film The Next Best Thing, playing Everett's sick, gay friend.

So, how was Madonna?

"She's very, very famous," he says. "She's so famous you don't expect her to be embracing; you'd think she'd be a little standoffish. I don't know if I want that kind of fame. She causes traffic jams."

Since Harris is now playing a phobia-heavy character on Stark Raving Mad, is he phobic about anything?

"Short-lived TV series," he says.