Ad Exec by Day …

Most days, you can find Dan Cronin writing copy for TBWA\Chiat\Day’s Nextel business. And every so often at night, flip to Late Night With Conan O’Brien and you can see him there, too. Cronin, 32, is also a professional comedian, who performs in New York comedy clubs and appears regularly in O’Brien’s comedy sketches.

A job at an ad agency can seem like a 24/7 commitment to some, but others have managed to squeeze in a second career. And, they say, one discipline often helps them succeed in another.

“If you’re a creative person, the more you’re doing, the fresher you are,” says Court Crandall, co-founder and creative partner at Ground Zero in Los Angeles. In his spare time, Crandall, 38, writes scripts—he has a credit on the Will Ferrell/ Luke Wilson comedy Old School, released earlier this year—as well as children’s books. “Screenwriting, particularly, encourages you to think about characters, makes you a better dialogue writer.”

Writing takes up much of Crandall’s spare time—a few hours late each night and on weekends—but none of his agency time. “If you’re trying to motivate the creative department, you can’t look like your allegiances are elsewhere,” says Crandall, whose first kids’ book, Hugville, is due from Random House in 2005.

BBDO’s Rani Vaz, who says she’s “most in her skin” when performing, devotes about a dozen hours a week to playing violin in a rock band, a string quartet and a piano trio. “It helps me to interact with writers and composers,” says the New York agency’s director of music and radio production. “And I think my ear is much more sensitized to what works musically.” But she’s had to compromise: After five years’ freelancing for the Joffrey Ballet orchestra and the Long Island Philharmonic, Vaz eventually decided that juggling nightly rehearsals and agency duties was too difficult.

Hal Dantzler, 42, of DDB in Dallas almost missed last November’s opening of his restaurant because he was on a shoot. But agency work comes first for the 42-year-old executive director of broadcast, who owns Hattie’s with his domestic partner—who runs the casual eatery—and director John Adams of Form in Los Angeles. “You have this discussion that the only way we can have this child is if I’m not the primary caregiver, because I know at any point I can be called for production for a month,” he says.

Dantzler, who’s at Hattie’s 10-20 hours a week, thinks the extra work pays off. “Any time you broaden your horizons, you gain insights you wouldn’t normally have that you can apply across both professions,” he says.

Travis Hopper, an account executive at The Richards Group in Dallas, says spending his free time as a songwriter and guitarist in a punk-rock-country band helps him relate to his creative team. “Writing a song and writing an ad are not all that different,” explains the 25-year-old. “You hope you communicate your message clearly.” And, Hopper says, his creative project helps win his team’s respect when he offers feedback.

“I said upfront, ‘If someone offers me a million dollars to sign my band, I think I’d be a fool not to take it,’ and they’ve been supportive,” he says of the agency. He’s lucky his client, grocery-store chain H.E.B, is a short flight away in San Antonio, but it’s not always a smooth transition from the office to hip venues around Dallas, where The Americanos play often. “There have been times when it’s Friday night and I’m here at 7, trying to get an ad out, and it’s hard to change my mind frame from work to band mode in an hour,” he says.

Though Cronin tries to keep his jobs in separate time blocks, sometimes he ducks out of the agency for a Late Night sketch. “I’ll say, ‘I need to play a fighter pilot and I’ll be gone for a while,’ ” he says. “As long as the work gets done, my bosses are incredibly flexible, and they’ve come to see me and cheer me on [at comedy clubs].” He’s also taken a brief unpaid leave to work on comedy-writing projects.

Thinking of taking a second job yourself? Hopper offers this advice: “It’s, Do you want to do it for the idea of ‘Everyone will think I’m cool,’ or do you love it so much that you need to find a way to make it happen? I really enjoy it, and I would regret it when I’m older if I didn’t pursue it.”