The CBS sitcom has grown to become the highest-rated show on US television since its launch in 2007, and is now broadcast in over 70 countries around the world, reported Digital Spy.
Parsons - who plays Sheldon Cooper in the sitcom - said that he never expected the show to take off in the manner in which it has.
"It's been a glorious surprise, the whole way. I knew from the beginning that I felt what we were doing was good work, because we shoot in front of a live audience, I knew they were enjoying it," Parsons said.
Parsons also compared Sheldon to his latest character Oh from the DreamWorks movie "Home", and that it was refreshing to play someone who is generally nice.
"You have no idea, the heaven it was to come from playing someone sort of anti-social, to someone who kind of wants to embrace everyone and wants to be loved. It was like a whole new set of muscles you hadn't stretched in a while."