Charles Martinet, the voice actor for Mario (and Luigi and Wario) has a pretty interesting story on how he came to voice the character. In 1990, Martinet was referred to by a friend about an audition to play a plumber at a trade show, so he crashed the audition without even applying for it just as the casting directors were putting away their equipment and finishing up for the day. He asked if you could try for the audition and the directors allowed him to, telling him he was "Italian plumber from Brooklyn named Mario" while mentioning that he'll also be a character in a video game and was instructed to make up a voice and make up a game as he auditions. This was apparently the moment where Martinet learned that he was voicing a video game character, video games were something he had no knowledge of. Martinet nonetheless carried on with the audition, coming up with the high-pitched, soft-hearted and friendly voice Mario has today, which he felt would be easier for children to hear. The directors were so enraptured with Martinet's performance, that they would tell him to keep going whenever he would stop. Martinet claims he kept on improvising for a good half-hour until the audition tape actually ran out! After it was over, the directors thanked Martinet for coming in and told him they would call him if he got the position. Martinet figured that meant he didn't get it and didn't expect to hear back from them, but one of the directors immediately got on the phone with Nintendo to tell them they had found their Mario and the rest is history.