A previous version of this film had Bill Skarsgard providing his own voiceover for his character in the style of a Mortal Kombat announcer before H. Jon Benjamin was cast for the final version; the trailer featuring Skarsgard's voiceover has mostly been scrubbed from the internet. In the original concept trailer, Boy's inner voice is taken from a cigarette commercial, with a voice similar to Sam Elliott's.
Samara Weaving was cast as June 27, but stepped down as scheduling conflicts and replaced by Jessica Rothe
The guitar-playing robot is The Robot from the original "Lost in Space" with slightly different head sphere.
Pete Davidson was originally considered for the role of Boy.