Not to be confused with Johnny Galecki, the actor for Leonard Hofstadter.
Johnny Miller is a major character and one of Penny Hofstadter's ex-boyfriends.
Johnny was born in 1980, the same year his best friend was born. He also used to be a Role Model when he was in Brooklyn, when he moved to Pasadena, California, he became a physicist. Surprisingly, he has some similarities to Sheldon, both of their fathers died when they were 14, they work at Caltech, and they are physicists. Johnny grew up with his caring mother, and a abusive father. In 2006, he met Leonard Hofstadter and his best friend, Sheldon Cooper. He used to have a girlfriend when he was in high school, but his father set him up with a unnamed male.