If you're not familiar, Keenan Cahill is a teenager from Illinois who has Maroteaux–Lamy syndrome, which sometimes causes physical features that appearance similar to those of dwarfism. Keenan has made himself famous by lip-syncing popular songs and uploading the videos to YouTube. In fact, he's even been joined by the original artists in some of the videos.

Keenan's latest video features him lip-syncing to Katy Perry's "Last Friday Night" with Dianna Agron, Darren Criss, Harry Shum, Jr and Jenna Ushkowitz of Glee.

Here are a few of my favorite Keenan videos featuring LMFAO, Brittany Spears, and Katy Perry.
LMFAO in Las Vegas...

With Brittany Spears at Atlantis Resort in the Bahamas...

Onstage with Kay Perry at the Wells Fargo Center in Philadelphia, PA...