I love the song. I still remember hearing it for the first time when as a child and my family was driving to our vacation spot in the summer of 1969 and my older siblings somehow convinced Dad to turn the radio to a rock station. They must have played that song a dozen times during the trip to and from vacation. Perhaps I like it for the memories it brings back of our last family vacation as a complete family. My oldest siblings were already 19 and 17 by that time and soon moved on to start their own lives. Also three of the six family members in the car that summer of 1969 have since passed away.

But the reason this weird pronunciation is so funny is because the rhythm (or meter) of the song requires the years to be pronounced "twenty-five twenty-five" and "seventy-five ten" and etc. else the song wouldn't have the correct beat.