Revealing mistake: During the fight between Garak and Worf near the end of the episode, a Jefferies tube door is knocked out of its frame to reveal the end of the set - a dark room with a wooden scaffold and various other pieces of equipment (slow-mo helpful but not required). (00:36:00)
Visible crew/equipment: When Mulder and Scully enter the abandoned mine through a doorway, the viewer can see at right in the distance a number of people sitting on a wall, and one crouching in front of the wall with what looks like a dog. They are sitting still, but there is still movement there. (00:16:00)
Continuity mistake: The age gap between Eric and Cory decreases as the series progresses. At the start of the show, Cory is in 6th grade and Eric is a high school sophomore, meaning they are four years apart, give or take a few months. By season 3, Cory is in 9th grade (confirmed by dialogue mentioning that Shawn, who is in the same grade as Cory, is 15 years old), and Eric is a senior, leading to an age gap of three years. The first episode of season 4 takes place a couple months after the end of season 3, with Eric and Cory returning from a summer Road Trip, but just two episodes later, Cory mentions that he is in 11th grade, while Eric is still barely out of high school, leading to an age gap of two years.
Revealing mistake: There are numerous times throughout the series where the supposed big city of Metropolis is actually just a back lot set and none of the buildings are more than a couple of storeys high. Quite often the green hills of Southern California can be seen beyond the set and between the buildings.
Continuity mistake: Up until Green No More in Series 2 (where the Green Ranger powers are destroyed), the Green Ranger's overshield constantly changes between solid-looking metal to flimsy-looking cotton. This is the most obvious difference between the Japanese and US footage.
Other mistake: Jack follows J. Edison Nash to a wine warehouse and watches as Nash punches numbers on a keypad in order to gain entrance to a private room. Nash punches the 6 and a beep is heard. He then punches the 8 and another beep is heard. During a close-up of Jack, four more beeps are heard, for a total of six. Jack says the number out loud - 862, which is only three digits.
Continuity mistake: In an interior shot of the detectives' vehicle, the car is a late 80s Chrysler (LeBaron or K-Car), obvious from the 'pentastar' logo on the steering wheel and the distinctive gauge layout. When the detectives walk away from the car, it is the homicide standard issue Chevrolet Cavalier.
Character mistake: Trivette hands the man in yellow a bullet recovered from the plane Walker and Alex were traveling on, which was shot down by an assassin flying a P-51 Mustang. This man, and later Trivette, mistakenly refer to the round as a "50mm," when in reality, Mustangs were equipped with M2 Browning .50 Caliber (12.7 mm) machine guns. (00:30:25)
Continuity mistake: In an earlier season Caine takes a young Peter to a place in the temple and explains that his mother is buried there. However in the series finale he shows adult Peter a picture that someone took months ago and Caine tells Peter that the woman is his mother and he's going to find her.
Continuity mistake: "A Stranger in Time, Part 2": Darien's arrival in 1993, shown in part 1, is recapped in part 2. But the director appears to have chosen different takes for the recap. Much of the dialogue differs substantially, and Selma's explanation that he's materialized in the ladies' room is left out altogether.
Continuity mistake: When Filburt first reads his fortune cookie, it says "Bad luck and misfortune will infest your pathetic soul for all eternity". But later on when he is walking down the street it says "Bad luck and extreme misfortune will infest your pathetic soul for all eternity". (00:03:25 - 00:04:25)
Continuity mistake: When Leo's son throws his watch against the wall, it breaks into several pieces, which bounce off a surface just below the camera frame (it's an odd look, but could be a table or the floor, as we don't see where on the wall the watch impacted) - then they fly off to the right. But in the next shot, most of the watch's pieces are falling to the floor, directly down, and in a group (the prop man simply held out his hand and dropped them into frame). (00:37:40)