Towards the end of the film, there is a picture of what appears to be the Hiroshima explosion hanging over Henry's nightstand. In the next shot, the picture is gone.
The boy who brings Henry's head to the pencil-making shop suddenly has glasses on when he faces away from the camera to enter the side door.
When Henry enters Mary's house, there is a large, distinctive "dent" on the top of his hair that disappears when he gets into the house.
The man's hands on the door at the beginning.
Henry's hands change position between two different shots while holding the brown paper bag as he stands in the building elevator.
Camera shadow visible, tracking into the light towards the end of the film.
At the beginning, when the giant "spermatozoide" appear, we can seen a invisible string on the right of the screen, pulling the prop.
Henry takes off the wrong shoe/sock to dry off.