The third season of the popular sitcom "The Big Bang Theory" on the American CBS channel still revolves around four lovely physics geniuses, Leonard, Sheldon, Howard and Raj, and the blonde beauty next door, Penny. The biggest breakthrough this season is the love affair between the nerd Leonard and the beautiful Penny. It is said that Leonard (Johnny Galecki) and the four of them returned from a three-month scientific expedition to the Arctic Circle, and Penny (Kaley Cuoco) finally showed her feelings for him. At the same time, Sheldon (Jim Parsons) learned that the major scientific discovery he made in the Arctic was actually a prank by Leonard and the three of them, and he ran back to his hometown in a rage. The three friends had to chase him to Texas and bring him home.