6 Facts You Didn't Know About 'The Big Bang Theory'
3 Of 6 Bazinga!
Sheldon's catchphrase is "Bazinga!" and Stephen Engel was the one who started "Bazinga!" It all began when Engel would play practical jokes in the writers' room, saying "Bazinga" instead of "gotcha."
4 Of 6 The Stairs
There is only one set of stairs leading up to Penny, Leonard, and Sheldon's apartments. The scenes where the actors walk up or down the three flights of stairs have to be shot in separate takes because the actors and the scenery needs to be reset after each flight.