The filmmakers use the song "House of the Rising Sun" throughout because the lyrics are in public domain, which helped them stay within their limited budget.
The decision for Justin Benson and Aaron Moorhead to also act in their film was largely an attempt to keep the budget down.
Shot in 18 days.
In the room where the math equation is on the blackboard, there's a globe in the corner which shows south east Asia and Australia. But they are not shown in the configuration of current geography because the Australia on the globe is connected to both Papua New Guinea and Tasmania, which last happened more than 12,000 years ago.
The totem poles were really tiny miniatures.