The Great Santa Claus Switch
The 1970 special The Great Santa Claus Switch featured a group of elves working in Santa's Workshop. They introduced themselves in the song "Happy Little Christmas Elves" as "Zippity, Skippity, Hoppity, Bing, Bong... and Fred."
Fred, performed by Jim Henson, was the only elf to realize that Santa had been replaced by an evil twin, Cosmo Scam, who was bent on filling the workshop with monstrous Frackles and ruining Christmas.
In the 1996 special Elmo Saves Christmas, a group of Anything Muppet elves become increasingly frustrated by the endless Christmas labor caused by Elmo's wish that he could have Christmas every day. Performers for the elves are Fran Brill, Martin P. Robinson, Kevin Clash, David Rudman and Joey Mazzarino.