Maybe this is a TV game show. Or stage show. Or filmed just for the internet, who knows? These guys have a powerful incentive to say a certain tongue-twister correctly. I bet they had to sign some kind of waiver.
What fabulous prizes could be worth this?
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There's another one with a lot of the same people here:
http://www.youtube.com/watch?v=5dEeltN3Q8o&mode=related&search=
In this one, they're subjecting each other to increasingly bizarre types of torture, while trying to remain silent in the library where it's all taking place. It starts slow, but give it a minute or two. The last contest especially is just too funny.
And if you like this kind of stuff, I recently discovered http://www.tvinjapan.com, where they constantly post odd video clips like these from Japanese TV.