I think this is the creepiest of all
http://www.youtube.com/watch?v=o2h5ym6ZlVY
That and Ichor Falls are of course classics.
As a sort of serious side note, I will say that I think the fact that a lot of childrens programming looks so creepy to adults shows a sign in the way perspective changes. Mr. Rogers for example was an amazingly popular children's entertainer, and well loved by (most) kids but to an adult, or those same kids grown up, they find him disturbing, thinking he seems like a pedophille, a seriel killer, or both. Barney, The Wiggles, Teletubbies, Noseybonk (

), Baxter from "The Great Space Coaster", Lazytown, and others all illicit similar reactions from adults... though I admit those puppets do actually seem like something that should be scaring children by any measure of common sense.