Jimmy Fallon during a recent "Tonight Show" appearance, "It's scary, man."

There's one scene, in particular, that will likely terrify moviegoers. Chastain debated whether or not she was allowed to share this factoid -- and then went ahead and did it. She told Fallon that someone on set said there's the "most blood that's ever been in a horror film scene."

The fake blood was so copious that Chastain was still finding it on her the next day. She recounted how she was finding it in her eyeballs. Yuck.

Watch below, starting around the 2:15-mark.

"It: Chapter Two" is the sequel to 2017's Teach Grant playing grown-up versions of the of The Losers Club.

"It: Chapter Two" is directed by Andy Muschietti and hits theaters Sept. 6.