Why Is SNSD's Sunny Laughing on "The Late Show with David Letterman"?

SNSD’s Sunny was shown laughing very hard in a screen shot of SNSD”s appearance on “The Late Show with David Letterman.” The performance was on February 1 (Korean Time), click here for more pictures of SNSD entering the “Late Show” studio.

When you watch the clip of SNSD’s appearance carefully one can find Sunny laughing while David Letterman says, “Our next guest, and by the way Regis thank you very much.” Then David Letterman continues by saying, “Our next are a very popular group in South Korea who have just released their first album in America. It is entitled ‘The Boys,’ please welcome making their network television debut, Girls’ Generation.”

Sunny can be seen in her “dance ready position” but when she is slightly shown on screen she begins to laugh with her head held down.”

Also, check out their performance and interview on “LIVE! With Kelly.”

Is that nervous laughter? Or did somebody pop a joke?