MARY GIBBS (Boo) makes an impressive acting debut as the vocal persona of a playful young girl who becomes the first human to enter the monster world. Born in Pasadena, California in 1996, Mary is the daughter of Pixar story artist Rob Gibbs and his wife Sue. She moved to the Bay area at the age of 1-1/2, when her dad joined the Pixar story team. Gibbs describes Mary as "a typical normal everyday kid who can sometimes be a bit of a ham and occasionally acts super goofy. She is energetic, good-natured and a non-stop talker like the Boo character." Mary was originally brought in to record some temporary scratch track screams and giggles when she was 2-1/2. At that time, her language skills were still in the gibberish stage and she was just on the cusp of forming real sentences. Director Pete Docter used puppets and other quiet toys to try and get the verbal performance that the character required. Instead of having Mary remain stationary at a microphone, the sound engineers followed her with a boom as she scampered around the room. It wasn't until a year later that the Boo character was set and Mary was told she had the part. Other recording sessions followed.

According to her father, "Mary has had a few real concerns about monsters in her closet, but basically she understands that monsters are good and helpful. Now that she's five and has seen promos and trailers for the film, it's just starting to sink in that she's in a movie. My wife recently overheard her telling her friends in pre-school, 'I'm in a movie.' In real life, Mary is blond-haired, has small eyes and no pigtails so there isn't much physical resemblance to Boo."

Mary recently started kindergarten and has expressed interest in pursuing additional acting roles in school plays.