The Billboard Music Awards wouldn't be complete without a party.

Christina Aguilera rose from the floor to join Pitbull onstage for his live performance of their high-energy track 'Feel This Moment,' a top ten Billboard Hot 100 hit.

The two artists also brought a surprise to the stage. The lead singer of the the Norwegian synth-pop band A-ha also popped up o stage to sing his group's original 1980's pop hit 'Take on Me.'

'Feel This Moment' features a sample of the popular track.

Watch Pitbull & Christina Aguilera Perform 'Feel the Moment' at 2013 Billboard Music Awards