Basically one of the characters says earlier in the movie that they got handpicked to be put on a waitlist to audition for a huge talent show. At the end of the movie after the credits he's on stage singing "All of Me" by John Legend but really ridiculous and over the top. Blake turns around but sees the kid is going complete HAM and then presses his button again and turns back around. Then Pharrell and Christina turn around and Adam begs him not to pick him. Christina gives her pitch and says "you've got a lot of personality and I can really work with that" (or something like that). He decided to pick Christina and then goes to give her a hug but then won't let go. It almost looks like he's trying to feel her up. It was a really funny moment and Legend totally played the comedy to a "T"
Xtina is certainly no stranger to acting! Besides starring in the award winning movie "Burlesque" with Cher, she landed a role on "Nashville" in addition to her acting on The Voice; she's definitely in character when praising Blake and Adam.
If you weren't seeing "Pitch Perfect 2" before, are you now?