It's Justice performing D.A.N.C.E. but not really. It features the radio version of the song mimed by Michael Jackson, Prince, Stevie Wonder, Rod Stewart (or is Barry Manillow?) and Rick James, bitch.
According to presenter Jimmy Kimmel, the track is apparently from Justice's self-titled album "†". You can see the Justice duo Gaspard Augé and Xavier de Rosnay making a cameo tuning the radio at the beginning. Kimmel introduced them by saying "Alright. This is going to be wierd". Indeed:
Justice's video for this song was so good, Kanye West decided to make his own version. Check out this crazy freestyle he had with Mos Def: