Anton Yelchin's final project; he died shortly after finishing his lines, but Guillermo del Toro refused to replace his recordings. which del Toro noted was a challenge for the show's recording engineers. Of his decision del Toro stated that the actor "was proud of what he did, and we were so proud of how he did it." Del Toro added that his experience as a father and Yelchin's young age were also factors that led to the decision.
When creating the show's narrative, Guillermo del Toro noted that he wanted a "bittersweet journey" for Jim, that he should deal with issues that most such "power fantasies" failed to address: "You can be in high school and you can have your problems, then you get all these powers and then you have a different set of problems. There is no such thing as a final great outcome."
Originally developed as a movie but was changed to TV series because Guillermo del Toro couldn't find a way to fit that much story into a movie.
In the first episode when Jim gets into his armor, you can see when the TV turns off that Dragons (2010) is on the TV.
The Gnome that Toby lets live in his dollhouse is named Gnome Chompsky after famous linguist Noam Chomsky.