It is the title character in Stephen King's 1986 horror novel It. The character is an ancient cosmic evil which preys upon the children of Derry, Maine, roughly every 27 years, using a variety of powers that include the ability to shapeshift, manipulate, and go unnoticed by adults. During the course of the story, It primarily appears in the form of Pennywise the Dancing Clown.
King stated in a 2013 interview that he came up with the idea for Pennywise after asking himself what scared children "more than anything else in the world", and feeling that the answer was clowns. King thought of a troll like the one in the children's tale "Three Billy Goats Gruff", who inhabited a sewer system.The character was portrayed in its Pennywise form by Tim Curry in the 1990 television adaptation, in the 1998 television adaptation by Lilliput, and by Bill Skarsgård in the 2017 film adaptation and its 2019 sequel It Chapter Two, which was released on September 6, 2019.