Strong choices had been made with regard to the appearances of the characters and the specifics of their world. Director Bird had equally strong views about the voices that would aid in bringing the characters to life.

He says, "I am not a huge fan of designing characters to have the look of the celebrity voicing it. I feel that’s a very limited way of thinking. I prefer to approach the whole issue by asking, ‘Who is the character and how does that character look?’ Then I find a voice to suit the character. I mean, Homer Simpson looks nothing like Dan Castellaneta, who voices him. I like to find a voice that compliments the design of the character."

Bird continues, "I look for actors with distinctive voices. In live-action films, actors can use their whole bodies to convey who they are. The challenge here is to make sure all of the nuances of character can come through with just the voice. That serves the animation as well. It you want the best out of your artists, you want to give them a soundtrack that’s inspiring. You also don’t want to hamstring the animators into any kind of visual acting—you want them to invent stuff to go with the voice. So the voice should inspire the animator, and the better the voice, the better the animation."

Filmmakers chose Jennifer Aniston, television’s Rachel on the long-running Nielsen hit "Friends" and star of several feature films, as the independent Annie Hughes. "She’s a play on the usual 1950s mom," says Abbate. "We updated her. She’s single, working, young and attractive. She’s far from your usual Donna Reed-type ‘mom.’"

"The thing I liked about Annie and this project," observes Aniston, "is that it’s not at all what’s expected. She’s more like a mom from the 70s than the 50s. She’s very strong, like a mother tiger protecting her son, Hogarth. She’s funny and really spunky, in that great kind of Laura Petrie way. There’s also a tremendous heart to the story. I’m really happy to have been involved in the film."

Grammy-winning musician and actor Harry Connick, Jr. was cast to voice the role of Dean McCoppen, a beatnik sculptor who owns a junkyard that serves as the giant’s temporary home. Abbate comments, "Dean is a outsider in this small, somewhat conservative town. Harry Connick was the perfect choice—he just exudes that cool cat kind of beatnik mentality. Plus, he has that southern drawl so he sounds like he’s an outsider."

"I had an idea immediately who Dean was," says Connick. "I grew up in the South surrounded by guys who see the world in different way. Artists, jazz musicians, crazy guys in New Orleans. I had a blast working on this project."

For Hogarth, Bird wanted a fresh young voice with a quality different from most child actors. "Hogarth needed to be innocent, but tough enough to be on his own most of the time. Hogarth has lost his father, plus he’s too smart for the kids his own age, so he’s developed a great imaginary world of his own making. He’s always on the lookout for nuclear monsters or invaders from outer space, but he’s also constantly rescuing animals who need a home."

Eli Marienthal, a then 12-year-old theatrical actor with several television and feature credits, filled the role of Hogarth. He says, "I think Hogarth lives in an imaginary world, so when the giant comes along, he’s sort of fulfilling Hogarth’s fantasy. I really think it’s more a story about friendship than just a story about a boy and a giant. I also really think that there’s so much of Brad Bird in Hogarth that there is no way I could have done it without him."

(Scott Johnston also comments on Hogarth’s powerful imagination and enthusiasm for life. He says, "When I look at Hogarth, I can get a sense of what Brad must have been like as a kid.")

For the voice of Kent Mansley, the government agent bent on discovering and ultimately destroying the giant, filmmakers cast feature film regular Christopher McDonald, for whom Bird tailored the role. Abbate says, "Christopher has that perfect combination of good looks and strength, plus he can also be funny, self-deprecating and even just plain evil—and that all comes through in his voice. We actually made it a point of designing Kent to look like the stereotypical perfect father so that he would really fit into the family of Annie and Hogarth. We wanted him to look like the all-American guy but still be evil to the core."

"I play Kent, and he’s pretty full of himself. He wants to break out of the bowels of Capitol Hill, where he has this little windowless office," elaborates McDonald. "I had done animation before, doing the voice of Jor-El for the series of ‘Superman.’ Your imagination takes over and the possibilities are limitless. But it’s also very challenging because it’s only the voice that comes through. In a way, it’s a little like Shakespeare, because the words are key."

For the key role of the Iron Giant, filmmakers signed actor and filmmaker Vin Diesel. Abbate explains, "In the beginning, the giant is really not able to speak—he wasn’t designed to speak. So his first words are very mechanical sounding. Toward the end of the film, his voice becomes more human. We were going to be electronically modulating the giant’s voice for that mechanical sound, but we needed a deep, resonant and expressive voice to start with. Vin’s voice is great. You can really hear his heart. He makes the giant imposing but still charming."

Diesel felt a kinship with the giant, saying, "The Iron Giant is misunderstood. His strength is the bane of his existence and despite the fact that he’s designed as a killing machine, he is really as simple as a child. I’ve always said that I feel like a bull in a china shop, and with the giant, he moves to scratch his back and buildings fall. Actually, I think we came from the same planet.

"I’m an animated actor, so to speak," continues Diesel. "I use my body, my hands, my expressions. And in doing this kind of work, all of that is irrelevant, all of that is erased. The voice—it was a luxury to just get behind the microphone and go to work."

To round out the cast, filmmakers hired an esteemed group of actors with an amazing and varied list of credits. Veteran actor and Tony-winner John Mahoney wore the stars as Kent’s boss, General Shannon Rogard. Familiar character actor M. Emmet Walsh gave the wild-eyed fisherman (who sees the giant fall into the ocean), Earl Stutz, his voice. Accomplished actor James Gammon voiced two of the townspeople, Marve Loach and Floyd Tubeaux, and Oscar-winner Cloris Leachman stepped into the shoes of Hogarth’s teacher, Mrs. Tensedge.