Goofs

At around 35 minutes the chair in Jasper's hands changes from being down on top of the other chair to up in a swinging motion.

When the invisible Griffin removes his glasses for Herbert, the eye-holes in the bandage are huge enough to see into. When he unwraps the bandage a moment later, the eye-holes are so small as to be almost non-existent.

When Robert Griffin is giving himself the blood transfusion he is pumping the syringe but not working the two valves that directs the blood from one body to another like what the doctor did earlier in the movie.

When the lifeless body of Doctor Peter Drury is moved off the examination table he lifts up a knee to help with the removal.

When invisible Robert Griffin has flour on his face, Jon Hall's eyes briefly become visible during the dissolve transition at the end of the scene.

When the Invisible Man gets out of bed at around 30 minutes he is standing next to the bed but his body is super imposed over the pillows on the bed.

When Drury gives Griffin the shot of whiskey while Griffin is invisible, it should have been seen going down his throat.

During the last half of the film, visible wires/strings are used to stage many of the invisibility effects, most notably when the invisible Robert Griffin lifts the unconscious Mark Foster up unto a table. And in three different close-up shots of Brutus (Dr. Drury's dog), we see a wire holding up the dog's muzzle.

Before Griffin decides to put flour on his face, his head is faintly visible while he's waiting for the pancakes.

At about the 38-minute time stamp, the invisible man come to visit Jasper. Behind him is a fish tank filled with water, but no sign of fish,

At exactly 30:48 the voices of both actors are clearly added in post production because the voices do not match. "A lot to do" "Yes, yes there is a lot to do" can be heard but sound completely different from the original dialog.