We're kind of obsessed with the pairing of Ariana Grande and Iggy Azalea, and their amazing mash-up of 'Fancy' and 'Problem' at the 2014 Billboard Music Awards tonight totally proved why.

Azalea started out strong with everyone's new favorite jam, 'Fancy,' bringing out Charli XIX to sing the chorus. As the blonde Australian rapper pranced around the stage in a plaid cheerleader-like outfit, the audience couldn't get enough of the tune and was seriously feeding off of the energy of the electric performance.

The set quickly switched gears and led seamlessly into Ariana Grande's performance of her hot new single, 'Problem.' Much like her iHeartRadio rendition of the tune, Grande killed it vocally, showing off her impressive chops as she rocked a mod-style, short black and white checkered dress and trademark high pony. Of course, Azalea did double duty during the performance, switching right into the rap on Grande's track, entertaining the crowd the whole time. And both ladies looked (and danced) flawlessly, rocking those choreographed hip-shaking moves that had the audience clamoring for more.