I really thought it was the "Turn the World Around" when I was younger... and I really feel bad about it. I really didn't like African Masks when I was younger. And really, the whole song is beautiful and I just feel terrible it creeped me out when I was younger...really I do.
Even though it didn't creep me out, seeing it when i was around 7 yrs old, i thought the masks were taking the place of the Electric Mayhem - and i would try to figure out which mask was supposed to be which EM member! (Since they kept singing "Do you know who i am?" i figured it was a guessing game) When the Muppets came in at the end of the number, they looked so happy to be "free".
As for my creepiest moment, it was the opening of Christmas Eve on Sesame Street. The ice skating Muppets always seemed so weird because they looked a bit different and their mouths didn't move but the creepy part was Ernie's barrel joke on Bert. Bert kept going on and on about "Ernie - you're going to get HURT!" and Bert ends up seeming really hurt at the end...Ernie keeps asking "are you okay, Bert?" and Bert either doesn't (or can't) answer.