Leighton Meester's birthday isn't until April 9, but Jimmy Fallon and his audience threw her a surprise party last night. Then the lady better known as Blair Waldorf tried to explain the show:

While pointing at a picture of all the cast in bed, she said, "My character was with him; who cheated with her, who's now dating him, but he still loves her. They had a thing; they had a thing; they had a thing; we had a thing; these don't have a thing because they're brother and sister." And really, that is the essence of the show. Clip at left.