Claim: Johnny Galecki plays a character with a Ph.D. in The Big Bang Theory.
Evidence: He is known for playing David Healy in the ABC sitcom Roseanne from 1992 -- 1997 and Dr. Leonard Hofstadter in the CBS sitcom The Big Bang Theory since 2007.
Leonard Leakey Hofstadter , Ph.D. , is a fictional character in the CBS television series The Big Bang Theory , in which he is portrayed by actor Johnny Galecki.