IT by Stephen King and the 1990 Mini Series of the same title review
The story revolves around a predatory shapeshifter which has the ability to transform itself into its prey's worst fears, allowing it to exploit the phobias of its victims. IT mostly takes the human form of a sadistic, wisecracking clown called "Pennywise". The protagonists are The Losers Club, a group of outcast kids who discover Pennywise and vow to destroy him by any means necessary. The miniseries takes place over 2 different time periods, the first when the Losers first confront Pennywise as children in 1960, and the second when they return as adults in 1990 to defeat him a second time after he resurfaces.