Bart's voice is provided by Nancy Cartwright, who voices several other child characters on "The Simpsons", including Nelson Muntz, Ralph Wiggum, Todd Flanders, and Kearney. While the roles of Homer and Marge were given to Dan Castellaneta and Julie Kavner because they were already a part of "The Tracey Ullman Show" cast, the producers decided to hold casting for the roles of Bart and Lisa. Yeardley Smith had initially been asked to audition for the role of Bart, but casting director Bonita Pietila believed her voice was too high. Smith later recalled, "I always sounded too much like a girl. I read two lines as Bart and they said, 'Thanks for coming!'" Smith was given the role of Lisa instead. On March 13, 1987, Nancy Cartwright went in to audition for the role of Lisa. After arriving at the audition, she found that Lisa was simply described as the "middle child" and at the time did not have much personality. Cartwright became more interested in the role of Bart, who was described as "devious, underachieving, school-hating, irreverent, clever". Matt Groening let her try out for the part instead, and upon hearing her read, gave her the job on the spot. Cartwright is the only one of the six main "Simpsons" cast members who had been professionally trained in voice acting prior to working on the show.