What causes fear of clowns?

Clowns have always had a dark side. After all, these were characters who reflected a funhouse mirror back on society; academics note that their comedy was often derived from their voracious appetites for food, sex, and drink, and their manic behavior.

Their mischief began to regain its sinister tone thanks to pop culture staples like Killer Clowns from Outer Space (1988), It (the novel, miniseries, and 2017 film), and Clown (2014).