Cowell 'can't wait' to judge fellow 'X Factor' judge

Demi Lovato will duet with Fifth Harmony in the 'X Factor' USA final - because she "didn't have anything else to do".

Show chief Simon Cowell - who is the group's mentor - joked it was "irritating" to have his fellow judge work with his act, but felt it best she had something to occupy her time because she has no contestants left in the competition.