Mitchell-Smith's very first passion was ballet. He studied as a child and even won a scholarship to dance with the School of American Ballet. While there on his scholarship, he was discovered by a casting director and his film career began in 1982 at age 12 when he played a younger version of the title character in Sidney Lumet's "Daniel". After a starring role in the 1984 film "The Wild Life", he was cast as Wyatt Donnelly in the 1985 teen film "Weird Science" by writer/director John Hughes. The film focuses on two nerdy teenage boys who create a woman of their own (played by Kelly LeBrock), as they are unable to find girlfriends.