An early music video for the song that was #1 at the beginning of October 1965, my senior year in high school.
I don't know when or where this video was shown- I don't remember it. But the song itself has one of those great hooks and riffs that live long in the memory. Two brothers of the original combo were from Ohio which may explain why this is the official rock song of the state of Ohio. It also is the unofficial fight song of The Ohio State University Buckeyes. (Wikipedia)
The way music changes from week to week is shown by the difference between "Sloopy" and the song it replaced at the top of the charts. Here's a video from the TV show Hullabaloo with Barry McGuire performing his hit. This performance I remember. It isn't easy to forget.
By the way, McGuire was one of the New Christy Minstrels before this one shot at stardom. In the early 1970s he became a pioneer in the contemporary Christian music scene.