Taylor Swift and the Backstreet Boys?! Sign us up! On Instagram Monday, frontman AJ McLean shared a new video jamming out to a mashup of his boy band's song Everybody along with T-Swizzle's new song Elizabeth Taylor from The Life of a Showgirl. In the caption of his video, he wrote: "Come on now you know one of us had to! @taylorswift !" Watch (below): View this post on Instagram A post shared by Alexander James (@aj_mclean) Cool!! Related: Taylor Inviting EVERYONE To Wedding...