Snerf was a monster created during Jim Henson's early years on television variety shows. It is essentially a little fuzzy tube with eyes and hair, who pops up and down. When Ideal Toys created the first licensed Muppet dolls, the three characters they chose were Kermit, Rowlf and Snerf. However, there's no evidence that the Snerf puppet was actually manufactured and sold.
After a while, multiple copies of the monster appeared at the same time, and they became "the Snerfs".
Four Snerfs appeared in the 1970 special The Great Santa Claus Switch. One of them identified himself in a song as "Snickery".
Originally, the Snerfs had round noses. In The Great Santa Claus Switch, they had beaks. In their Herb Alpert and Muppet Show appearances, they had trumpets for noses.