The Big Bang Theory S05E05
Duration: 59 sec.
Created by: Chuck Lorre & Bill Prady
Sheldon characterizes his relationship to Leonard as "Schrödinger's friendship", in the sense that Leonard is simultaneously his friend and mortal enemy (as he may or may not attend Wil Wheaton's party). When Sheldon tries to explain the paradox to Penny, she gives an approximate description: "...] there's this cat in a box and until you open it, it's either dead or alive or both [...]".