John DiMaggio's voice will give you déjà vu. You won't recognize the tall, sandy-haired actor, but his big voice will ring familiar. A conversation with DiMaggio might leave you scratching your head, wondering just who he is.

Inside the immense panel rooms at San Diego Comic-Con, the story is different. When DiMaggio walks onstage, the crowd lets out a collective roar. They know him, perhaps as wise canine sidekick Jake from Adventure Time, or maybe vice-laden robot Bender from Futurama. It could be one of any number of cartoon characters he has played over the years.

DiMaggio is part of a contingent of actors whose IMDb pages burst with credits, though they don't elicit the instant recognition enjoyed by their on-camera comrades. They are humans who play anthropomorphic characters, adults who play children and teens. Their knack for breathing life into fictional heroes and villains can turn films, animated series and video games into hits. They are voice actors, and even the best known in the business lead fairly anonymous lives.

That is, until they hit fan conventions. Go to Anime Expo or San Diego Comic-Con and you'll find plenty of animation buffs tracking down the stars of the cartoon world. They line up for autographs and hang around panel rooms for a chance to meet their favorite stars.

It's a weird dichotomy, a life strange enough to spawn a documentary — which is part of the reason DiMaggio is at Comic-Con. He's producing a feature called I Know That Voice, an inside look at the voice-over business, which includes interviews with folks you'll recognize from shows such as Animaniacs and SpongeBob SquarePants. Some of them also appeared on the movie's Comic-Con panel, which drew a crowd large enough to fit inside a midsized L.A. concert venue. The response to the panel, and the coming documentary, was thunderous.

DiMaggio also voices Jake from Adventure Time

DiMaggio also voices Jake from Adventure Time

DiMaggio got into the voice-over game back in the 1990s, when he was living in New York and working the stand-up comedy circuit. Futurama, the Matt Groening–created sci-fi comedy, was his big break. After that, DiMaggio racked up the credits.

He has a hard time remembering all the characters who bear his voice. “Sometimes people remind me of stuff I've done and I have completely forgotten,” he tells the Weekly.

In animation, actors are booked for a few hours of work at a time. Frequently, they'll record as a group — “It's like gathering every class clown around and putting them in a booth together,” DiMaggio says — but it's not unusual for them to go solo. On busy days, they'll hop from studio to studio, playing characters that will appear on competing networks. Maybe they'll have a few video game sessions crammed into the schedule as well. (Those new cinematic games have been a boon to some voice actors.) Back at home, they'll churn out a few more audition recordings to keep the work coming.

“It's a career, and everyone is still trying to build to the next level to maintain this,” says Stephanie Sheh, who has spent the past 15 years in the voice-over world. Sheh has appeared in original animated series — Care Bears: Welcome to Care-a-Lot and Peter Rabbit among them — but she's best known for her work in dubbed versions of anime titles. Sheh has handled English-language roles for dozens of characters who first appeared on-screen in Japan.

In the dub, or ADR, realm, actors like Sheh spend time alone in a studio watching a video screen as they try to match the lip movements — called “mouth flaps”— of the animated character. It's precise work; not everyone can do it. Sheh, who was an anime fan before she entered the industry, excels here.

She doesn't go to conventions all that often. If travel is involved, it can take too much time away from the weekly grind of auditions and recording sessions. When she's at events like these, though, her meetings with fans can be poignant. “What I do for a living doesn't save lives,” she says. “That doesn't mean you don't touch people.”

The heavy workload that voice actors take is, more than anything, a means of survival. Voice actor Dee Bradley Baker breaks down the nitty-gritty of pay on his blog, IWantToBeAVoiceActor.com. Scale pay, the minimum set through SAG-AFTRA negotiations, is common. Of course, that only applies if you're union. Non-union gigs vary.

For voice actors, the real world and the world inside the convention can be drastically different.

“While it's cool that we have these fans, when you go to a convention, you can get lost in this idea that you're some kind of celebrity,” Sheh says. In reality, “It's a small sect of the audience keeping track of who the voice-over people are.” Celebrity generally isn't part of the voice actor's day-to-day life.

“Occasionally, people will hear my voice and ask me if I'm an actor or something,” Baker says. On the phone, his voice is clear, his phrases well-considered, his enunciation flawless but not over-the-top. “I don't think I sound like a normal person, even when I'm speaking with words.”

Dee Bradley Baker voices Perry the Platypus on Phineas and Ferb

Dee Bradley Baker voices Perry the Platypus on Phineas and Ferb

If you hear Baker on TV, in fact, chances are he will be making a creature noise. It's work that suits him. Baker has been a fan of sci-fi and monster flicks since childhood and has a love of paleontology and biology. His hobby is taking photos of the flowers and bugs that inhabit his neighborhood, and then posting the images to Instagram.

And that keen interest in other species, real and imagined, has helped Baker carve out a niche for himself as the go-to guy for creature sounds. He plays Perry the Platypus on Phineas and Ferb. He recorded the sound just once, but it's repeated throughout the show. He has provided strange alien voices in every incarnation of Ben 10, including a whopping 17 characters in a single episode. Even one of Baker's more verbose characters, Klaus on American Dad, is a fish whose tone bears little resemblance to the actor in real life. For that role, Baker throws on a German accent, which he picked up after studying the language and living in the country.

“It wasn't a calculated career path for me,” Baker says. He simply liked to perform and found he was able to land jobs doing so, whether it was at a theme park or as the guy who delivers singing telegrams.

Baker records auditions in a studio he built in his Burbank garage and dispenses advice to aspiring voice-over artists on his blog. Every now and again, he heads out to conventions like San Diego Comic-Con.

“It's an exhausting ego blast,” he says of the conventions. He sees these appearances as another sort of performance, one that can last for nine or 10 hours a day as he meets fans and goes back and forth between his own voice and those he's created for various characters.

It's work, but it's fun work. “Having a few thousand people to perform for is a real treat,” he says.

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