The film was conceived and co-written by Joshua John Miller as a way of dealing with the death of his dad, Jason Miller, who had starred as Father Karras in The Exorcist (1973).
When Tina becomes hyper-focused on the fly buzzing around the room, it was a spur of the moment ad-lib, not a digitally generated insect.
Angela Trimbur improvised her entire dance sequence. She slammed energy drinks to get in character and worked herself up for the frantic dance.
When the characters are sucked into "Camp Bloodbath", it was scripted that they stepped into "a Technicolor world." The writers were initially horrified when they showed up on location and discovered that the crew had taken their words literally and decorated the forest with colorful artificial flowers.
Director Todd Strauss-Schulson had always envisioned Alia Shawkat as Gertie, but he got the runaround from her manager, so he found her email address and brazenly contacted her directly.