You will unlock ELIOT as a playable character after completing the Grand Finale Challenge. This achievement is glitchy - moves that counted for some people and gave them the achievement have not counted for other people. ELIOT is the default character during the Grand Finale Challenge and when you play the moves from Satisfaction. If you pass them (by achieving at least a "Nice" rating) you should unlock this achievement at the end of the song. If not, try playing through Satisfaction on Easy, since virtually every move in that song is a robot move. If that doesn't work play Soulja Boy on Easy. The move Robocop is considered a robot move, and this unlocked the achievement for me at the end of the song.