'Glee' Cast Joins Viral Star Keenan Cahill For Katy Perry Lip Synch

07/05/2011 05:31 pm ET | Updated Sep 04, 2011

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.)"

Criss is the only Gleek to who seems to know all the words to the hit, probably thanks to his cameo in the official music video.

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