The Big Bang Theory Season 7 Episode 15: The Locomotion Manipulation
5 second plot: It's Valentine's Day and everyone is celebrating it in their own way. Sheldon kisses Amy on the lips. And meets a new friend that loves trains as much as he does. And Leonard and Penny almost kill Raj's dog.
5 second review: Sheldon is hilarious. He makes himself totally unpopular by ignoring Amy on Valentine's Day, but then kisses her and with that, gets himself back in the game.