David Howard Thornton was the sixth person who auditioned for Art The Clown after Mike Giannelli retired from the role and acting altogether. During the audition, he began miming tasting his beheaded victim's blood, but then added salt to it to improve its flavor. This is what won him the role.
David Howard Thornton, who portrays Art the Clown, has previous mime experience, which he utilizes in his performance.
The ambulance that drives past Dawn as she listens to the radio broadcast in the car was unplanned. That was a real ambulance that drove by.
Director Damien Leone created Art The Clown because he felt that the 2010s lacked an iconic horror clown. However, he purposely made Art as different from IT's Pennywise as possible. For example, Art doesn't have hair, wears all black & white, uses weapons, and doesn't speak.
The underground tunnels used in the film were part of the abandoned Seaview Hospital. These tunnels were used to transport the dead out of sight of the other patients, where they were to be cremated.