'Glee' Goes Viral: Darren Criss, Dianna Agron, Harry Shum and Jenna Ushkowitz Join Keenan Cahill for Katy Perry Lip Dub (VIDEO)

Get a Gleek and four "Glee" cast members in a room with a camera and an iPod, and you might get something like the latest viral video from Keenan Cahill.

The YouTube star is famous for his lip-sync videos, which have gained him enough internet fame to have the likes of 50 Cent, Pauly D and Katy Perry perform with him. Cahill must be a big Perry fan, because he covered her one more time with a lip dub of "Last Friday Night (T.G.I.F.)."

But Cahill had some friends help him out with this one: "Glee" stars Jenna Ushkowitz (Tina), Dianna Agron (Quinn), and the newly-promoted series regulars Harry Shum Jr. (Mike) and Darren Criss (Blaine) joined in on the lip dub fun. The gang looks like they're having a blast with some creative dance moves, and Agron's rocking the new 'do.

Why choose the "Glee" stars for the video? Simple: Criss makes a cameo at the beginning of Perry's video (his first "Glee" song was "Teenage Dream") and Kevin McHale makes a big appearance as well. Sadly, it looks like McHale couldn't make it to the Perry party.

Criss is no stranger to the world of viral videos, as he rose to internet fame before his "Glee" gig with the Harry Potter spoof musicals "A Very Potter Musical" and "A Very Potter Sequel," for which Criss wrote all the music.

Check out the video below: