Viral video star Keenan Cahill is back with another lip synch, this time adding the power for the "Glee" cast.

Stars Dianna Agron, Jenna Ushkowitz and newly minted cast regulars Harry Shum Jr. and Darren Criss joined Cahill backstage during the "Glee Live" arena tour to record a video to Katy Perry's "Last Friday Night (T.G.I.F.)"