Leonard is named after actor/producer Sheldon Leonard and Nobel Prize in Physics Laureate Robert Hofstadter. The part was originally offered to Macaulay Culkin but he turned it down as he did not like the pitch. Johnny Galecki was originally asked to play the role of Sheldon Cooper but thought he would be "better suited" for the character of Leonard. Leonard is one of four characters to appear in every episode of the series, along with Sheldon Cooper, Howard Wolowitz, and Rajesh Koothrappali.