Donnie Dunagan spent 25 years in the Marines. He was a decorated Vietnam War veteran who rose up the ranks quickly—13 promotions in 21 years, as he recalls—and held such honors as being the youngest ever drill instructor and receiving a Bronze Star and three Purple Hearts for his service. And when he retired as a Major in 1977, he was finally able to talk about a little secret he'd kept from his colleagues all those years: Long before he was barking orders at new recruits, they'd all definitely heard his voice before, as children, when he was far less menacing. Major Dunagan was the voice of Bambi.

Dunagan was a fairly successful child actor in the late 1930s and early '40s, having shared the screen with Boris Karloff and Basil Rathbone in both Son of Frankenstein and Tower of London. But when he was 6 years old, he got the biggest role of his acting career—voicing the title character in Disney's newest animated feature, Bambi.

Dunagan, with his expressive face and wide eyes, was hired to be both the model and voice of the young fawn. His mother took him to the zoo to see a deer in person, and then he spent months working with the animators so that they could create the character. Dunagan told DVDizzy about some of the ways the Disney illustrators would coax him into making funny faces:

When Bambi was sitting in a thicket feeling sorry for himself, being foolish, I was asked by the 'Drawing Men' to look like something real bad had just happened to me that made me mad. I was having the time of my life then, so really I had a hard time putting on an 'unhappy face.' The men drawing me were waiting for me to do it better. Then one man asked me about any recent bad experience such as a spanking, bad food, etc. I told them that my Mom had given me something called castor oil last week.... it was grim. "Donnie, pretend that you just had a double dose of castor oil." And I did; my face crunched up and eyes grew mad. So when you see that cute scene in 'Bambi,' the thicket kiss, you can call that the 'castor oil kiss.'

The toughest scene for the young Dunagan to record—and the hardest scene for audiences to watch—was the obvious one: The scene where Bambi's mother is shot by a hunter. "They told me to call out 'Mother … Mother … Mother,' and I did," Dunagan told Chicago Parent. "The film makers made me repeat this several times, and I didn't get it right until they told me that my mother was in the studio and was in danger. They told me to call out to her, and I really thought that she was in danger, so it sounded more authentic."

But once the movie was released in 1942, Dunagan's film career ended. He'd hoped to work with Disney again, but they slowed production after the attacks at Pearl Harbor. Dunagan went on with his childhood, and enlisted in the Marines when he turned 18. And by that time, he'd stopped talking about his animated past.

"I am a commander in the Marine Corps boot camp, and there are hundreds of recruits I am responsible for—I just thought to myself 'I don't think I want all these young Marines to start calling me Major Bambi,' and I kept my mouth shut," Dunagan said recently on NPR's StoryCorps.

But now that he's retired? He relishes his role in the classic childhood movie. "Is there any incongruity in being a tough old Marine and loving Bambi? No, no," Dunagan told the Houston Chronicle. "I go down the street now, and when some old Marine who knew me before yells, 'Hey, Major Bambi!' I love it to death."