On his debut in 1979, he was known as the Television Monster, a character that was fixated on television. He had antennas standing out of the top of his head, and his eyes would whirl around when he watched television. After that stint through season eleven, producers worried that he would be a negative influence on their easily influenced viewers, and changed him into the worry-wart character that he been Telly ever since.
Telly is a triangle lover, and has a pet hamster Chuckie Sue. He has been known to uncontrollably pogo stick around Sesame Street, often causing havoc with all that gets in his way. This episode is one of the ones shown on Sesame Street Unpaved.
His first appearance on Sesame Street, after the Television Monster stint, was with guest star Joshua Redman playing the violin, while Telly played his tuba.
Telly is puppeteered by Muppeteer Martin P. Robinson. There is rumor he was named after film and television star Telly Savalas, though this is untrue; his name uses the British slang for a television, telly.