What is a novelty record?

Hit Novelty Records

Part of our trivia team went to Tune Trivia last week, and were in the running until the final question: "A Sesame Street character had a top 20 hit back in the '70s. Who was the character and what was the song?"

I feel qualified as a Sesame Street expert, having owned many Sesame Streeet LPs (back then, we didn't have VCRs, kids) and learned to read one sponsor at a time. Still, I missed the trivia question, whose answer is on the page linked above....

I was a little surprised by how liberal the linked author was in his definition of "novelty," including the McCartneys' "Uncle Albert/Admiral Halsey" alongside the Chipmunks, Johnny Cash's "A Boy Named Sue," and others. So what, exactly, makes a song a novelty? Why aren' they around anymore?