Christina Aguilera and Ellen played a game of "Heads Up" when The Voice star stopped by the show on Monday. Ellen had Aguilera impersonate other female singers, which Ellen had to guess based on Aguilera's excellent singing impressions. 

Aguilera nails most of them, but gets caught by a few and just speaks the song lyrics. On the last one she can't remember a song but does recall a fact about the singer. That's not so much an impression, but it would make for a really fun version of karaoke for people who don't like singing.