A duck voice lesson in Episode 3095
"Hello-Quack-Quack" is a Sesame Street song written by Tony Geiss with the intention of appearing in Episode 3095, but was ultimately cut.
In the episode, Mr. Snuffleupagus participates in Sonny Friendly's "Duck for a Day" show and must accurately portray a duck to win the grand prize. He receives help from Big Bird's duck friends Duffy and Gracie, who help him learn to walk and talk like a duck.
In the original script, Telly Monster was the duck-to-be and receives one lesson how duck quacks can translate to different phrases. With a song, Telly demonstrates how he's learned to speak duck and converses with his feathered teachers.