Feist will be guest-starring on the 39th season premiere of Sesame Street on August 11, and her performance of a tweaked-for-kids "1 2 3 4" is already online. Kids will no doubt recognize the hit song from ipod commercials: [videoembed size="full_width" alignment="center"][/videoembed] Also stopping by the Street will be Will Arnett, Jessica Alba, David Beckham, Heidi Klum, Neil Patrick Harris, ...