Dayman....Whoa-oh!

If you have ever watched It`s Always Sunny in Philadelphia then you likely know that one of the many, many highlights was Charlie discovering the song "Dayman":

Simply awesome. So via Gawker, this is simply blowing my mind.

I have three pertinent questions:

1. Why are Japanese Kindergarten students singing "Dayman"?
2. Why is there a drawing of Peter Griffin in the background?
3. How high is the American grad student who is obviously teaching these children?