After Richard Coyle, who plays Father Blackwood, ended a sermon by saying, "Hail, Satan," a peculiar tradition was formed. Anytime anyone sneezes on set, all 300 cast and crew members use the expression "Hail, Satan" instead of "God bless you."
"It turns into this massive echo," production designer Lisa Soper told Thrillist. "You can hear it everywhere. We even made crew T-shirts saying 'Hail, Satan!'"