Continuity mistake: "11 Days to Zero": A saboteur on an overhead scaffold hastily sprays an X on the top of Nelson's car with white paint. In later aerial shots, the X is composed of 2 perfectly straight, thick lines stretching from corner to corner of the car's roof. No way was that X made in a few seconds with a spray can. (00:03:00)
Continuity mistake: Throughout seasons 2-4: When the series went to color in the second season, the Seaview was redesigned with only one set of observation windows. But stock footage of the old multiple windows continued to appear for the rest of the series, usually with the film dyed blue.
The City Beneath the Sea - S1-E2
Continuity mistake: Seaview's windows form 8 horizontal rectangles in 2 rows across its bow. But the interior sets have windows that form vertical rectangles, and they're much closer together than they are in the exterior shots. (00:02:30)
The City Beneath the Sea - S1-E2
Continuity mistake: Seaview is on the ocean floor investigating the underwater city. Two inserted stock shots then show it up near the surface at periscope depth. In the next shot, though, it's back on the bottom again. (00:43:15)
No Way Out - S1-E12
Continuity mistake: When Victor tries to get into sickbay, the guard stops him, pointing a rifle at his chest. But in the very next reverse angle shot, the rifle is again in its original position in the guard's hands, pointing at the ceiling. (00:35:10)
No Way Out - S1-E12
Continuity mistake: When Anna tries to kill Koslow, Victor spies on her from behind the ventilation grate. The ribbons fluttering on the duct cover disappear when the shot switches to Victor's point of view. (00:46:50)
Continuity mistake: Captain Crane removes a failsafe key, which is hanging outside his uniform collar, from around his neck. It wasn't there in the previous shot. (00:10:30)
The Cyborg - S2-E4
Continuity mistake: To expose The Cyborg duplicate of himself, Nelson disrupts the nerve controls on the computer facsimile's left hand. But The Cyborg Nelson's right hand is the one that subsequently malfunctions. (00:45:20)
The Cyborg - S2-E4
Continuity mistake: At the end, Crane shoots The Cyborg Nelson in the forehead. It clutches at its completely intact face and falls down. We cut to crew reactions and then back to the fallen cyborg - and now its head is nothing but a jumble of circuits. Were those delayed-action bullets in Crane's gun? (00:46:40)
Continuity mistake: Nelson spins the roulette wheel. We see a close-up of the wheel slowing down. Cut back to a full shot, and now the wheel is spinning faster than ever, even though no one has touched it. (00:42:15)
Continuity mistake: Nelson takes the captured assassin's knife and says that Alicia was killed with one just like it. But he can't possibly know that. He never saw the body or the weapon. Only Crane was with Alicia when she was murdered, and Crane, still missing in action, hasn't been in contact with Nelson. (00:42:15)
Continuity mistake: When a scuba diver (Pilar Seurat) approaches the flying sub, her regulator is on the left and her dive knife is on her right leg. Also, she activates the underwater voice transmitter with her left hand. Once aboard the flying sub, her regulator is on the right side, with the knife strapped to her left leg. Also, she's right-handed. The film of Seurat - more likely her stunt double - swimming towards the sub was likely "flipped".
Continuity mistake: Kowalski's uniform and hair are soaked after sealing the hatch from the hull breach, but his uniform is bone dry and hair properly combed when he immediately reports to the Seaview's Control Room.
Continuity mistake: Interior shots of the flying sub sows the sub rocking violently but exterior shots show the sub lying still on the sea floor.
Continuity mistake: The shot from the rear of Kowalski and Nelson shows Kowalski holding the scanner. The next scene Nelson asks Kowalski what is on the scanner and then tells Kowalski to pick it up.
Continuity mistake: During the battle a railing on a pirate ship falls off, only to be seen in the next shot intact, then missing in a subsequent shot.
Continuity mistake: The video set turns on before Admiral Nelson activates the "on" switch.
Continuity mistake: When the four divers exit the Seaview, each has a flashlight. When the reach their destination only three have flashlights.
Continuity mistake: Part of Admiral Nelson's torn uniform changes position on his shoulder as he is being checked out in sick bay.
The Wax Men - S3-E24
Continuity mistake: When Captain Crane is shooting the wax crew members, his pistol runs out of ammo, locking the slide open. The next shot shows Crane still shooting without reloading a new magazine.
