The Wolf Man falls into the ice caverns beneath Frankenstein castle. Larry Talbot awakens the next morning wearing shoes, which The Wolf Man didn't have on.
During Larry Talbot's first transformation into the Wolf Man, he goes from wearing light-colored night clothes to a dark shirt and pants. When he awakens the next morning, he's back wearing the pajamas.
Talbot is in the hospital having had an operation for a head wound. On the night of a full moon, he tears his bandages off and turns into the Wolfman and escapes into the town dodging through the shadows, but he's now in outdoor clothes instead of pajamas.
When the monsters are wrestling on the floor, a book falls off one of the machines behind them. In a later scene of the fight, the book is back on the machine.
In the long shot of Frankenstein's monster carrying Elsa up the stairs, her long flowing gown hangs down to his feet; to avoid stepping on it, he clearly has to take wide strides up the steps. Then there is a cut to the monster as he reaches the top of the stairs, and here Elsa's gown is completely wrapped around her body.
When the moon rises to transform Talbot in the hospital, moonlight is shown moving across the floor then up the wall to his bed. A rising moon would cast its light first on the wall, then move down the wall to the floor as the moon rose above the horizon.
Talbot's body shows no sign of decomposition when the grave robbers open his tomb. But it is explained that, being a werewolf, Talbot cannot die. Since he wasn't really dead, he did not decompose in his coffin.
In the final fight scene, just as the Wolf Man makes his final jump, his left shirt sleeve pulls up, and you can see Lon Chaney Jr.'s arm, which has no make up on it.
During the fight the Frankenstein monster throws a heavy electrical box with the Wolf Man standing on it. The strings used to move the box can clearly be seen.
When Lawrence Talbot first introduces Dr. Mannering to the Baroness, she inexplicably addresses him as Mr. Mannering.
The Baroness calls him Doctor Mannering, she does not say Mister.
After Inspector Owen ends his telephone call with the police sergeant, he and Dr. Mannering discuss traveling to Llanwelly. At the end of the scene, Dr. Mannering says "care for a cigarette"?, but the audio is missing.
When the monster is being recharged in Dr. Frankenstein's
laboratory by Dr. Mannering, he is mouthing the words, "Thank you, Dr. Mannering!" but all the monster's audio was edited out.
After Larry Talbot frees Frankenstein's monster from the ice, he asks the monster where Dr. Frankenstein's journal is as they walk into the remains of the castle, but his mouth does not move.
When Freddy Jolley is in the mausoleum at the beginning of the film, but just after he turns toward the center of the room, you can see the power cable for the oil lamp taped to, and running up his right arm at his wrist. Normal oil lamps at the time would produce insufficient light for certain shots, so electric lamps were used. There is an obvious difference in brightness from the shots outside of the mausoleum and the interior shots. The power cable is visible again as he sets the lamp on top of the Larry Talbots's center crypt.
When Larry and Maleva have arrived in Vasaria, seeking Dr. Frankenstein, they are ordered out of the pub. As they move toward the door, the camera's shadow is clearly visible on the half-wall adjacent to the door as they are about to exit.
Despite the early scenes being set in Cardiff and its environs not one character has a South Wales accent.
The innkeeper refers to the river being above the castle and the dam below it, then suggests that blowing up the dam will drown those in the castle. Later it is shown that the dam is above the castle.
The innkeeper says: 'here are the ruins. In here are all of them. Here runs the underground stream that drives the turbines that Frankenstein installed. But the water comes from up here to the dam below' Therefore, he is saying that the water source is above the dam, not that the castle is above the dam.