Buchanan states that the lead-lined house will prevent detection of the radiation that Dr. Stieg uses to power the creatures. Yet later, Dr. Stieg indicates that the radium power source will draw the injured Harris creature like a magnet even though the radium is still inside the lead-lined hideout.
Dr. Walker warns the authorities that there is grave danger of radioactive contamination if they bomb Buchanan's hideout. But when he breaks into the laboratory, Walker actually grabs the radium power source (how he knows where to find it is unexplained) and hurls it out a window.
When Dave goes to Chet's home, we see a name tag with 'Chet Walker' just above the doorbell. It's only there as he rings the doorbell. All other shots show a plain doorbell with no tag.
The scar on Dave's forehead after the atom brain surgery has healed way too fast as if it were months old rather than just a few hours.
Jet planes are supposedly shown patrolling the city air space in order to detect a house emanating radioactivity. It's ludicrous to think that an aircraft traveling at supersonic speed would be able to isolate radioactivity in a single building.
About 8 minutes in the detectives are inspecting the crime scene and point out a bullet hole in the wall from a hand gun. The hole is about the size of a silver dollar but should only have the circumference of about a dime.
During the 8mm film showing the behavior of the dog, the animal is obviously blinking its eyes after it has supposedly obediently received a command to sleep.
As Dave falls for the last time, he is seen to blink. He is supposed to be dead.
Upon finding her daughter crying over a broken toy, a mother screams hysterically, which is patently ridiculous.
The creatures supposedly don't have any memory of their living existence yet they know how to drive a car.
In an early scene in the lab, Dr. Walker (Richard Denning) describes the chemical sample taken from one of the atom brain killers as having "enough radioactivity to kill a man." Yet when he and his partner and the D.A. leave the lab after testing the sample to talk to the press and then head out, they leave the sample out and the lab door open and unguarded.
Despite knowing how the creatures are controlled (having seen the X-rays) and that the only way to stop them is to sever the electrical connections, Walker never tells the cops to aim for the head.
Explaining the apparent use of dead people in the murders, Dr. Walker tells the police of Michael Faraday's electricity experiment on a frog's leg. In fact, it was Luigi Galvani's experiment in the 1780s. Faraday was born in 1791.