Coulrophobia was the irrational fear of clowns. Luke Smith noted this psychological disorder by its proper name when a clown began appearing to the students at his school. Sarah Jane Smith was a known sufferer from an early age. She began suffering from the phobia in reaction to a toy clown that used to hang near her bed. She claimed that its unnatural gaze terrified her at night. As an adult, she discovered that the toy had, in fact, been manipulated by the Pied Piper to instil this fear in her. She later overcame it because of the concern for her son, Luke, was stronger than her fear.
Darius Pike had coulrophobia as well. On his sixth birthday, his father hired a clown called Mr Floppy Fun Pants to come to his party. The young Darius was terrified by his antics. He later said it was the worst birthday party he ever had in his life. This fear was exploited by the Bodach, who gave him a dream in which he was locked in Mariah, his antique car, with clowns. (TV: Dream-Eaters)