Kid Rock
Or, even though it came later in the program, perhaps the unexpected but not exactly live-feeling appearance of A-Ha's Morten Harket during Christina Aguilera and Pitbull's rendition of "Feel This Moment"?
Morton Harket can sing like a motherfucker. I don't think he needs lipsyncing. Don't know about the other two.
Diogenes of Sinope: "It is not that I am mad, it is only that my head is different from yours."
Arnold Judas Rimmer, BSC, SSC: "Better dead than smeg."
Arnold Judas Rimmer, BSC, SSC: "Better dead than smeg."