Glow-Worm

The sketch involved Kermit humming the tune while sitting on a wall as a worm crawls to him and taps him. Kermit sees the worm and eats it, followed by another worm who shows up and does the same thing. The third time a worm shows up, Kermit catches it early, but it gets longer and longer until it's revealed to be the nose of a larger entity (often Big V), who eats him.