When some people think of clowns, they picture brightly coloured hair, big smiles, and lots of laughs.
Others find clowns creepy with evil intentions hiding behind a cheerful, gruesome mask. The intense fear of clowns is called coulrophobia.
At the forefront of modern-day clowns are Joseph Grimaldi and Jean-Gaspard Deburau who excelled at making people laugh, but in real life, Grimaldi died as a penniless alcoholic and Deburau murdered a boy in the street.
They were not unusual. John Wayne Gacy, a professional clown, turned out to be a notorious serial killer. He used to say "A clown can get away with anything." Since then, the perception of the clown seems to have taken a turn.
People may also feel uncomfortable with clowns because the painted-on and exaggerated face pose a false expression, and that breeds distrust.
Sigmund Freud called this disconnect "uncanny". This "uncanny valley" is something computer animators and robot creators have difficulty with.