Many of those who know Neil Patrick Harris from his breakthrough role as TV's Doogie Howser or his appearances in such movies as Undercover Brother and Starship Troopers may not be aware of this young actor's impressive theatrical credentials. Praised for his performance as Mark Cohen in a tour of Rent, Harris went on to corner the market on the role of Tobias Ragg in four separate staged concert presentations of Stephen Sondheim's Sweeney Todd. After co-starring in a recording of Sondheim's little-known score for the TV musical Evening Primrose, he made his Broadway debut as a replacement in David Auburn's Proof and, more recently, did a stint as the Emcee in the Roundabout Theatre Company's long-running revisal of Kander and Ebb's Cabaret.

Now he's rehearsing two roles, the Balladeer and Lee Harvey Oswald, in the Roundabout's Assassins -- the first Broadway production of the controversial Sondheim musical that had a brief Off-Broadway run in 1990. The show begins previews at Studio 54 on March 31 and is set to open there on April 22. When I spoke with Harris via telephone in early February, he was just preparing to leave L.A. for the frigidity of NYC.

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THEATERMANIA: Neil, you're becoming something of a Sondheim specialist.

NEIL PATRICK HARRIS: Yeah, I'm riding the Sondheim wave! He found out about me through that first Sweeney Todd I did in L.A. Then I did the other Sweeneys, then the Evening Primrose recording, and then the Assassins workshop. He's a swell guy.

TM: After you did Sweeney in L.A. with Kelsey Grammer, you did it with the New York Philharmonic and then with the San Francisco Symphony.

NPH: Right -- and then I did it again in Chicago at the Ravinia Festival. So I tooled around with Sweeney Todd for a while. It was a great experience but a little surreal. I was put into the role of "classical soloist," which has not been my track!

TM: Was Rent your first major musical theater gig?

NPH: Yes. I had done some theater in L.A. and in New Mexico when I was younger. Living on the West Coast, I had sort of appreciated theater from afar. I would come to New York and see shows, and I would usually buy the album of a musical and listen to it before I got to see it. That was the case with Rent; I got the album when it first came out and I really responded to the music. Jonathan Larson had the miraculous ability to create songs that sound more impressive the more you listen to them. When I finally saw the show in New York, I loved it.

TM: Tell me about the experience of performing the show.

NPH: It was the second national tour. We started in La Jolla while Michael Greif was still the artistic director there, so we had a nice, full, four weeks of rehearsal and then did it for a while in La Jolla -- three months, I think. Then we came to L.A. and did it for another four months. It was an awesome experience. To sing the "Seasons of Love" reprise after Angel has died...you're standing at the lip of the stage, looking out at the audience, and everyone is weeping. That's a powerful thing to get to do every night. As an actor, to have a real acknowledgement that you're moving people is pretty rare.

TM: I know that you played Mark Cohen. Who else was in that production?

NPH: Roger was a guy named Christian Menna, who is a recording artist in Canada. Our first Angel was Wilson Cruz. And Jim J. Bullock was Tom Collins; they went for a whole different take on the role!

TM: It's great that you're doing another Sondheim musical. I was listening to Evening Primrose just the other day. Isn't "Take Me to the World" one of the most beautiful songs ever written?

NPH: Yeah, it's really amazing. You know, I'd never done a recording of anything before -- not in a studio like that. I walked in and there was this huge orchestra with Paul Gemignani conducting. Jonathan Tunick was walking around to the people in the orchestra saying, "Do this," "Add a quarter beat here," "Play a little quieter there." Then Theresa McCarthy and I went into our own little both and we just sang! I was kind of overwhelmed by the whole thing. I mean, I consider myself an actor who has decent vocal tone and decent pitch. I'm uncomfortable singing karaoke or in any sort of benefit or concert situation where a song is out of context. For me, the singing is sort of an extension of what's going on within the character.

TM: And that's what makes you perfect for Sondheim shows. Talk to me about Assassins.

NPH: Well, this is an election year, so I'm anxious to see how the show goes over. People have strong reactions to the characters that we're depicting because they come with their own historical baggage. Sondheim has a great way of making you sympathize with potentially bad people -- like Sweeney Todd. To humanize these assassins, to really question why they do what they do and who they are instead of just labeling them as insane people, makes for a fascinating show. And I'm a huge fan of the score.

TM: You're playing the Balladeer and also Lee Harvey Oswald. Those roles were assigned to two separate actors in the original production. Does the fact that you're playing both reflect some specific concept that director Joe Mantello has?

NPH: We haven't started rehearsals yet, so I'm not sure how Joe wants to do it. I don't quite know if one character becomes the other, if one is the other the whole time, or if they're two separate entities. It'll be interesting. I'm very excited because I thought the Balladeer track lacked a little drama and the Oswald track lacked any sort of musicality, so to get to do both in one show will keep my short attention span occupied!

TM: You were quoted recently about the fact that you've done Broadway shows before but only as a replacement. The comment came across as somewhat negative and it looked like it might have been taken out of context, so I thought you might want to clarify what you meant.

NPH: Yes, I would. I certainly didn't mean it in a derogatory way. When you're with a show from its inception, you're not sure if it's going to be a success. You go through a long interpersonal process with the entire cast, then you start previews, and then the show comes out, good or bad. But when you step into a show -- like I did with Cabaret, which had been running for five years -- it's really just a matter of rehearsing for a couple weeks with the stage manager and dance captain, and then you're sort of thrown into a show. It's like jumping onto a fast-moving train. That's why I've been anxious to do a show from scratch. My favorite part of the whole process is the rehearsal period, because that's when you really get to interact with the other actors and see how they work in a closed environment where you're free to explore and fail. When you're stepping into a show, the parameters are kind of already set and there's not as much at risk.

TM: Two more questions: Do you have any plans after Assassins, and what are some of your dream roles?

NPH: I don't have anything lined up. I'm anxious to see how long this goes and what happens from it. As for dream roles, I've always wanted to play Barnum because I'm a circus guy; I juggle, I do trampoline tricks, I swing on a trapeze and do other things like that here in L.A., so the tightrope is right up my alley. But I hope they don't revive Barnum soon because I'm too young for the part. I need them to revive it in 10 years, when I'm 40!