Peter Gallagher and Mariska Hargitay Peter Gallagher and Mariska Hargitay

On his first day on the set of Law & Order: SVU, Peter Gallagher had one very important mission — and it had nothing to do with memorizing his lines or remembering his blocking.

"Mariska [Hargitay] and I did a selfie for Kathryn, my daughter," Gallagher tells TVGuide.com, "and she texted back and said, 'Dad, this is the coolest thing you've ever done.'"

Although the longtime actor is already considered "cool" in many circles for his work on Covert Affairs and, most memorably, as the beloved Sandy Cohen on The O.C., it's his latest role that has won him some serious brownie points at home. "I'm like the only New York actor I know who has never done an SVU," Gallagher says. "I was like, 'We got to fix that!'"

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Gallagher does just that on Wednesday's episode (9/8c, NBC) when he debuts as Deputy Chief William Dodds, the tough, no-nonsense head of all of the special victims units in the NYPD. "He was somebody who came up through the ranks and you could see how he's a character that could go one way but I really believe he wants to see all his units succeed. He wants to see Sgt. Benson succeed," Gallagher says. "He just has a certain specific style of how things should be done."

Indeed, Dodds and Benson get off to a rocky start when a bike messenger creates a video diary of his troubles with the opposite sex as he begins to commit violent acts against young women across the city. The case, which quickly becomes front-page news, couldn't come at a worse time for Benson, whose son Noah was taken to the emergency room at the end of last week's episode. "I think that he sees himself as a great coach and I think he sees that Sgt. Benson is a talented officer and investigator," he says. "Part of his job is making sure that the activities of all those units contribute to the over-reaching interest of the police department and what needs to be done."

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Ripped-from-the-headlines cases such as this one-- which is based on the May 2014 Isla Vista killings that left six dead — is one of the reasons Gallagher was attracted to Law & Order: SVU. "The most fun I have acting is when the stories are contributing to the world we live in," he says. "I like that SVU doesn't shy away from that."

While some might shy away from an aging series, SVU also appealed to Gallagher precisely because of it's long run. "You have the luxury of being in a show that has quite a track record and such a loyal following. It reminds me of one of the first jobs I had in New York, in the original company of Grease and I played Danny Zuko and I did it for a year. I didn't know at that point that it was unusual to do a show for a year until I did a bunch of flops after that that lasted 10 minutes," he says. "There's a good chance that there will be an audience there for your work, at the next performance or the next episode and it allows people to be busy with getting the job done instead of necessarily worrying every five seconds if somebody is going to pull the plug tomorrow."

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It's this mentality that keeps Gallagher so busy. In addition to his recurring role on Law & Order: SVU, the Tony nominee is getting ready to return to the Broadway stage this spring opposite Kristin Chenoweth in a revival of the classical musical On the Twentieth Century. So when he's not busting Benson's chops or playing a dramatic hostage scene, he's taking tap dance classes and working on his vocals. "I'm going to be on Broadway in a couple of months so I got to make as much money as I can," he jokes of his current balancing act. "It is a great contrast. ... It's good for your soul."

And that's not all. In addition to SVU, Covert Affairs and his upcoming five-month stint on the Great White Way, Gallagher also recently worked on HBO's upcoming comedy series Togetherness from writer-directors Mark and Jay Duplass (The Mindy Project). The gig is just his latest foray into comedy following How I Met Your Mother and a most surprising turn on Comedy Central's Kroll Show earlier this year as Bobby Bottleservice's gigolo mentor Sage. "What's very nice is to have that balance of shows that are scripted, like Covert Affairs... and SVU. And then you have shows like the Kroll Show and Togetherness which are scripted but it's a different style where you're free and encouraged... to improvise," he says. "What I really enjoy is that I'm not just doing one kind of thing, whether it's TV or theater or film or comedy or drama. It keeps me interested."

While some actors might want more downtime in between Covert Affairs' action-packed 16-episode seasons, the busier Gallagher stays the better. "Why would I not do it if someone's interested enough to have me do it?" he says. "At some point, that phone will stop ringing and until then, I still love what I do and I want nothing more than to do that with people I admire and respect in a role that I feel I can maybe contribute something to."

Law & Order: SVU airs Wednesdays at 9/8c on NBC. Are you excited to see Gallagher on the series?

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