The last scene in the film was re-shot six months after principal photography. For the reshoot, Jack's feet were framed out of the wide shots because actor Caden Stillwell had outgrown the shoes he'd worn in the earlier scenes.
The grunt of the mythical creature described in the bedtime story was created in post-production using a combination of two sounds: the bellow of a white rhinoceros, and a wet towel being wrung out.