U uberkriegr Guest Jan 10, 2008 #1 Because the voices sound like a higher pitched verson of his voice
G Grand Poobah Guest Jan 10, 2008 #2 Yes, he was King Friday, X the Owl, Daniel Tiger, Lady Elaine, the cat and others.
M Mr. Stiggo Guest Jan 10, 2008 #3 He voiced most of the major puppets, but I can't recall which ones specifically.
B Billy C Guest Jan 10, 2008 #5 yes - he was the king - I don't think he was the cat I believe that was the girl on the show