This is some sort of promotion or unofficial music video for the song 'Why Do You Let Me Stay Here' featuring Joseph Gordon-Levitt and Zooey Deschanel. The two star in the movie '500 Days of Summer' together and Zooey's band She And Him are the group behind this song.
It's a pretty cool dance sequence that reminds me of super old classics where actors were always triple threats. I had no idea 3rd Rock From the Sun guy could dance so well. I also didn't know Ms. Deschanel wrote such lovely tunes.
Here it is!