I have been a huge fan of Anna Kendrick's since New Moon's post theatre scene. It doesn't hurt that she's Oscar-nominated as well. She was on Dave Letterman this week promoting her new movie Pitch Perfect and performed what will always be known as "The Cup Song" to most people.
Here's her interview. The Cup Song starts around 6:17.
Right away I had to know how she did it - so cool! Some of you may be familiar with this cup thing. I guess it's been around for a couple decades but I think the singing part is new.
I think this is the original video from Lulu and the Lampshades
And this is the basic breakdown of how to do the cup trick
And here are the lyrics to the song from Lulu and the Lampshades' blog