Entertainment Tonight's "Big Bang Theory" special. Twelve incredible seasons of behind the scenes secrets and ET was there from the very beginning. Plus, the stories from the set you haven?t heard. Who had a secret romance? What?s really under Sheldon?s couch cushion and how they filmed around a star wearing a leg cast. Then, the cast before ?The Big Bang.? When we first met, Kaley Cuoco, Jim Parsons and Johnny Galecki. Entertainment Begins and Ends with ET.