Though audiences never saw what the monsters in Bird Box looked like, designers who worked on the film have given us a peek at what one would have looked like in a scene that was cut from the film.
As reported by The Wrap, creature designer and sculptor Andy Bergholtz (who also worked on A Quiet Place) posted mockups of the creature on Instagram with an explanation of why it was cut from the film.
Spoiler warning: spoilers for Bird Box ahead.
Bergholtz said that he designed “3 or 4 variations” of what one of the monsters would have looked like the cut scene. The scene in question involved Sandra Bullock’s character experiencing a “dream/nightmare sequence” while pregnant. He clarified that the visions each character saw when encountering a creature would differ from person to person depending on their fears, so Bullock’s would assume the form of a “twisted, demonic baby creature attacking her.”
Source: IGN.com Bird Box Monster From Cut Scene Revealed