Murderous clowns have quite the reputation, but with the rare exception of Pennywise in It and It Chapter Two, they’ve haven’t made much of a splash in mainstream horror over the last several years.

The lobby of Renaissance Dallas North Hotel is stately, with purple orchids and velvet couches, but down a long hallway, I can spot the clowns. More than 100 have gathered in Dallas, March 3-7, for ...