On The Big Bang Theory, Amy was away at Princeton for a research fellowship and she and Sheldon were missing each other. Although they frequently checked in on Skype to say hello Sheldon was also hanging out with his colleague, Dr. Ramona Nowitzki.
Ramona was giving Sheldon quite a bit of attention -- making him laugh, taking him swimming, bringing him lunch and asking him how long his girlfriend was going to be gone. All the signs were there that Ramona had a crush on Sheldon and although his friends could see it, he couldn't. So, he just went ahead and asked her. When she said, "What if I were?" Sheldon went on to list all of the reasons why that would be a bad idea and in the middle of that list Ramona kissed him.
Taken aback by this unexpected smooch, Sheldon excused himself, got in a cab, headed to the LAX airport and boarded a plane for Princeton. When he knocked on Amy's door and she opened, he was down on one knee with a diamond ring. When he asked her the question, "Will you marry me?" we were all on the edge of our seats but we'll have to wait until next season to see what Amy's answer is.