I didn't really want to assign characters except for Rainbow Dash for B.o.B.'s rap section buuuut turns out Twilight edges towards "being Jessie J" unintentionally so I'll just go with it. I like this outcome even if it took quite a while (FOOOOOREEEEEEVEEEER) to make :l

Twilight Sparkle as Jessie J and Rainbow Dash as B.o.B. in
"Price Tag" - Jessie J (Ft. B.o.B.)