I had to research thsi as much as any other radio story. I haven't watched Sesame Street in a few decades. the characters are called the "Yip Yips." The Sesame Street website describes them as " interplanetary visitors from Mars who valiantly explore our world despite their frequent terrifying encounters with everyday objects like telephones, clocks, and computers." they debuted in 1971 with a telephone skit and first met the radio in 1975.
I posted this because of their very instinctive attempts at tuning the radio. The radio pictured looks like a 1940s GE or RCA model. They have a visceral reaction to each station instinctively; just like people do but with a verbalization I think we all have internally. Yup. Nope.