Gabriel Bateman (Lights Out (2016), American Gothic (2016)), and Jacob Tremblay (Room (2015), The Predator (2018)) are sought-after for a leading role.
Scott Speedman (Underworld (2003, The Strangers (2008)) is Schoonmaker's top choice for a major role.
The on-screen role of the father in the film is an amalgamation of Schoonmaker's own dad and actor, Ethan Hawke. The "Rules For a Knight" displayed on the fridge is an easter egg appreciation nod to Ethan Hawke's book of the same title.
The Making of The Mummy magazine book featured in the movie as a prop item was a real-life item Schoonmaker purchased when he was a kid when the The Mummy (1999) was released in May of 1999; displaying the Visual Effects ILM did on the film.