S. Krishnamoorthy, better known by his screen name Madhan Bob, is a Tamil comedian and actor. He started his film career as a musician and then became an actor. Apart from appearing in supporting roles in Tamil films, he also appeared in the Sun TV comedy show Asathapovathu Yaaru as one of the judges. His debut film was Vaaname Ellai. He also taught music to M. M. Keeravani.

Bob was the eighth child in his family, so he was named Krishnamurthy, which also happened to be his uncle’s name. There was a lot of confusion in the house, so they changed his name to Madan. His's brother’s name is Padmanabhan aka Babu. Both started a music group called ‘Madan and Babu’. Soon, Babu became Bob, and that is how director K. Balachander introduced him in his first film.

During the shooting of Mappillai, Bob was injured in an accident. His assistant was also with him. When the car was nearing Vagaikulam, a dog crossed the road. In order to avoid hitting the dog, the driver applied a sudden brake. Because of this, the car capsized. Bob, his assistant, and the driver were seriously injured. However, Bob managed to break the glass door and save the driver and his assistant. The three were taken to a hospital for treatment. After the treatment, Bob participated in the shooting.