Creepy Yearbook

I was with my wife, our friends and their little 4 year old boy. I happened across a yearbook on the shelf and noticed that it was from 1976. Thought it to be odd, I opened it to discover that the yearbook was otherwise normal (long hair, individual pictures and pictures of sports and music groups) with one exception. Everyone in the book were dressed as clowns and what made this creepier was that the pictures were all in black and white. Knowing that my friend would be a little unsettled by this, I teased her by asking her son to point out his favorite clown and he emphatically said "that one". She was then irritated with me.