Continuity mistake: During his lecture on the brain, Professor Frankenstein draws the medulla oblongata on the black-board twice. (00:05:45)
Continuity mistake: The brain that Frankenstein draws on the blackboard in the first scene is different from the one behind him as he is seated and lecturing. Check the shading on the brain stem. (00:05:55 - 00:09:35)
Revealing mistake: In the classroom Frederick stabs himself in the leg with a scalpel. Look closely and you can see the thick pad covering his thigh inside his trouser leg. (00:11:10)
Character mistake: When Herr Falkstein introduces himself to Frederick he tells him he has come 5,000 miles to bring him his great-grandfather's will. The ancestor in question was supposed to be his grandfather, not great-grandfather. (00:11:53)
Suggested correction: Victor is Fredrick's grandfather, but not the one who died. Baron Beaufort von Frankenstein died, leaving the estate to Fredrick. Beaufort is his great grandfather.
Factual error: The movie is set in Transylvania, but the natives all speak German and with German accents (probably an homage to the book, but still incorrect). (00:14:30)
Continuity mistake: As he's about to depart at the train station, Friedrich leans in to try and kiss Elizabeth good-bye. He's mere inches from her nose when the shot cuts, at which point he's suddenly standing more than a foot away from her. (00:16:00)
Audio problem: When Frankenstein first opens the door to the monster-making room, the rusted handle breaks into two pieces, but when he throws them down, only one piece can be heard hitting the floor. (00:28:15)
Continuity mistake: When Frankenstein releases the monster from the experiment bed, he reaches for the third bar (over the monster's thighs) first, but the fourth bar (over his lower legs) is already open. All of them were closed when they left the monster in the lab. (00:46:50 - 00:53:55)
Continuity mistake: During Inspector Kemp's visit at the Frankenstein manor, Frankenstein is playing darts while he is having his conversation with Kemp. He throws the first dart at the bottom 10, but by the time he throws the second dart at 7, the first dart he threw at 10 is now at the bottom of 18. (00:56:20)
Continuity mistake: At the castle, Dr. Frankenstein throws darts while talking with Inspector Kemp. The shot of the darts hitting the board does not match with the shot where Inspector Kemp takes the darts back from the board. (00:58:50)
Visible crew/equipment: After the monster catapults little Helga from the seesaw to her room and she is tucked into bed, it is possible to see the wire that was used to pull the covers up (when her parents enter the room). (01:06:25)
Continuity mistake: During the scene where the blind man, Gene Hackman, is serving soup to the monster, the blind man spills 2 large ladles of soup onto the monster's lap. The blind man then burns the monster by lighting his thumb, thinking it's a cigar. The monster screams, and breaks through the front door, leaving the blind man's cottage. When the monster leaves the cottage, there is no sign of the spilled soup on his clothes. (01:08:50 - 01:10:55)
Continuity mistake: In the scene where Inga, Fredrick and Igor throw the net over the monster, Inga sticks the syringe of the sedative in the monster's back but does not push down on the top, yet the monster still falls over. A few seconds later when she collapses on the monster, you can see all of the fluid inside spray out. (01:12:05)
Revealing mistake: One of Peter Boyle's teeth on his lower jaw was painted black for that "broken grin" look. It can be seen reflecting in some scenes: when Frankenstein enters the cell with the monster and it cries, and later when the monster screams while killing the jailer. (01:15:30 - 01:28:40)
Revealing mistake: For most of the opera house stage presentation, the monster is a full head taller than Friedrich. During the tap dance, however, they're the same height. Although the camera angle/depth of field used tries to disguise this by keeping Gene Wilder in the foreground for most of the shots, it's still apparent that Peter Boyle isn't wearing his probably-impossible-to-dance-in platform shoes during the sequence. (01:24:00)
Continuity mistake: As the townspeople gather to storm the castle, the clock in the town square shows 10:30. When the Inspector steps out of the building to address them, the clock over his shoulder shows 10:00 PM. (01:28:45)
Audio problem: As Frankenstein lures the monster back to the castle with the violin, if you watch very carefully, some of his bow movements don't match the length of the sound that is heard. (01:35:30)
Continuity mistake: When Inga, Frederick, and Igor reach the secret library, Frederick reaches for the door knob to grasp it with his right hand, but the view from inside the room showing them entering has Frederick's right hand opening the door without using the knob.
Continuity mistake: When the casket slides off the wagon, breaks open and cracks a couple of its wood slats, the arm from the body is not protruding from it until Igor and Frederick come up to it in the next shot.
Continuity mistake: When Dr. Frankenstein introduces himself to the monster with a soothing "Hello, there", his right hand is on the restraint over the monster's chest. The next shot shows the doctor placing his hand on the restraint again.
