Judging by the reaction of the crowd, Lovato definitely stepped up to the plate and delivered.
The singer later gushed about the opportunity, writing on her Twitter:
… That just happened….. Thank you SO much @JessieJ for having me on stage for Bang Bang… It was an honor!
— Demi Lovato (@ddlovato) December 4, 2014
Did she really slay it? Watch her performance in the video above and then sound off in the comments.