The Big Bang Theory - 3x15 - The Large Hadron Collision 2010-02-08 Comedy / Romance Jim Parsons - Sheldon Cooper , Johnny Galecki - Leonard Hofstadter , Kaley Cuoco - Penny Leonard can only bring one guest on a trip to see CERN's Large Hadron Collider (the world's largest and highest energy particle accelerator) in Switzerland on Valentine's Day. 25 TV-14