: Skarsgård can actually move his eyes in two different directions independently, a trick that startled co-star Bill Hader on set when he realized it wasn't a post-production effect.

Because the child actors naturally hit growth spurts during the two-year gap between films, production had to use expensive CGI to "de-age" them for flashback scenes.

: Jeremy Ray Taylor (young Ben) grew 9 inches taller between movies, and Finn Wolfhard (young Richie) also saw significant height and facial changes.

The film reportedly features one of the bloodiest scenes in cinematic history.

: Lead actress Jessica Chastain requested the intensity herself, aiming for a "Carrie on steroids" effect. She had to be covered in the cold, sticky substance for the remainder of that production day for continuity. 2. Digital "De-Aging" Technology

: His iconic, creepy smile was also achieved without prosthetics or digital enhancement. 4. Casting Influenced by the Kids

While much of the film relies on CGI for its scares, some of Pennywise's most unsettling features were performed naturally by Bill Skarsgård.

The child actors had significant input into who played their adult counterparts.