This seems the perfect time to revisit this list, since the trailer for the remake of It (2017) landed this week. Check it out, and you'll understand immediately why clowns can be...terrifying.
In cult-television history, scary clowns have also long been a staple of storytelling. The circus or carnival is a frequent setting of popular genre series (including The Evil Touch, The Fantastic Journey, and Tales from the Crypt), and clowns have appeared again and again to terrorize our slumber.
So tonight, turn down the lights, close the door, crawl into your bed, and watch this episode about a clown and "prince of laughter..."