What is this line about Wayne Newton's penis from?

For some reason a memory popped into my head today from fourth grade. One of my friends was telling some joke (that he probably heard from much older kids and didn’t understand himself) and he said “You can see Wayne Newton’s penis for 100 dollars, or you could buy a shirt for 30 dollars.”

What is this from? Is this featured in a movie somewhere? What was he talking about?

This may shed some light on the subject. I personally wouldn’t touch it with a 10 foot (not inch) pole. :wink: