Deliberate mistake: When the dome is blacked out and blocking Chester's Mill from the sun, there should be no light at all in the forest, yet it's lit as if under a full moon. (01:10:40)
Deliberate mistake: When the news program is discussing Gyrich's assassination attempt on Xavier from the series finale of the original animated series, he's shown to have his classic look of auburn hair and sunglasses. However, when this scene occurred, Gyrich had black hair and was not wearing sunglasses. This was done deliberately to match the character design of the original series prior to the final 6 episodes, when Saban took over and redesigned much of the show's look.
Containment - S1-E11
Deliberate mistake: Sunny is the teams SAW (squad automatic weapon) gunner. He carries an FN MK46 which is a special operations version of the M249 SAW. The MK46 unlike the M249 only takes belt-fed ammunition from 100 or 200 round "nutsacks." On this mission Sunny is wearing a chest rig with STANAG mags and no nutsacks. He has no backpack for extra ammo either. He hands off his MK46 to the Jason whose staying behind and no nutsacks. Plus he doesn't take Jay's HK416 rifle in the swap. Usually people swap one for one. (00:31:15 - 00:32:00)
Deliberate mistake: They show footage of Max and Larabee scouting out the entrance to a bank. This same footage was used in the earlier episode "The Treasure of C.Errol Madre".
Deliberate mistake: When Joey and Jonathan get in Joey's car at Metropolis (just before heading to the police station), the car has headrests. When they get to the police station, see Lance Gessler leaving and then follow him, the car no longer has headrests. Obviously removed so as not to obstruct the actors.
Deliberate mistake: There's at least two episodes (Season 1's "Captive Hearts" and Season 4's "Sanctuary, Part 1") in which a character shows video footage of the X-Men and various supporting characters in action, but the footage is merely clips from previous episodes.
The Last Temptation of Cory - S3-E9
Deliberate mistake: When Cory calls Topanga from Missy's phone, he starts having a conversation with her as soon as he finishes dialing her number, with no time for the lines to connect.
Winning Through Intimidation - S1-E15
Deliberate mistake: In the actual card game, attacking the castle ring would not be allowed, but this is probably done in order to enhance the show for kids.
Deliberate mistake: In the restaurant after their daughter finishes talking to Niko, Erik turns the tablet device around and sets it on the table to talk to Niko. From his perspective, he is looking down at the screen. But in the other shots from Niko's perspective, where he is a life sized hologram, his figure is shown looking up and meeting her eyes. But from her perspective it should look like he's looking down at the table.
Deliberate mistake: When Roy and Moss are in Jen's office talking about her slipping up, the computer monitor disappears from her table in the wide shots so you can see the actress.
Suggested correction: It's there the whole time. It's a thin monitor and it lines up with Roy's leg, so it might have been hard to see.
Destination Moon: Part 2 - S3-E10
Deliberate mistake: The shot of the plane landing in Syldavia at the start of the episode, after the recap of part one, is merely the exact same shot of the plane landing in Syldavia at the start of the previous episode. Note the vehicles on the ground are completely identical and the plane, as well as its movements are also identical. (00:25:00)
Deliberate mistake: When Dominique is creating a Tinder profile for Fiona (an app Fiona admits she doesn't use), she manages to use Fiona's phone to take a picture of her, create a profile, and quickly get three matches, all within a span of 25 seconds. Downloading the app itself would take longer than 25 seconds, much less agreeing to its terms of service, and verifying the email or phone number associated with the account. (00:45:15 - 00:45:39)
Deliberate mistake: The last season touched on Infinity War happening - this season jumps forwards a year, meaning that we should be one year into the "blip" (or snap), with half the universe missing. But The Team is all together, and the world/universe is utterly unaffected. Largely a byproduct of disagreement between the film and TV sides of Marvel, plus scheduling vagueness meaning they couldn't risk spoiling Endgame if they came back on the air before that was released. But considering the show is 100% part of the MCU, that's a pretty massive contradiction.
The Last Temptation of Barry Allen, Pt. 2 - S6-E8
Deliberate mistake: There's an awkward moment during Cecile and Kamilla's escape from Bloodwork's minions where Cecile doesn't close the door for several seconds so the cameraman can walk through as they follow them.
Deliberate mistake: As Chief Vickery, in present time, patrols Wind Gap in his car he passes by the barbershop. From his POV, through the car window, we see four men sitting outside. The same men were also seen in Episode 01, but from young Camille's POV as she and her sister pass by the barbershop in 1992. The show hid a load of easter eggs and signs throughout all episodes. They would hardly make such a mistake. More likely, the repeat was to underline Vickery's backward, stepfordian attitude.
Deliberate mistake: The footage of sharks swimming past the base windows in pairs is immediately recycled twice. (00:09:34)
Deliberate mistake: In the opening of seasons 2 onwards, there is a photo of Olivia outside the Church with the family. This is a scene from Season 1 Easter Story. However, it had to be from an outtake because the position of Erin, the absence of Jason, is different than what is shown in the episode. It's just something I noticed when I identified from where the shot was taken.
Mercy Moment Murder Measure - S1-E7
Deliberate mistake: When Abraham throws the secret note into the fire, he crumples it up before tossing it in. But then we see a shot of the note lying open and flat on the log before burning. Not only would the note not be able to uncrumple itself, it shows no sign of being crumpled in the first place. This was obviously done deliberately so the audience could read the note one last time.
Deliberate mistake: After Bud overhears the plans for Flipper, he decides to hide his dolphin. When he boards the skiff, there are two flipped wide shots before they head out. Note the reversed dock, launch, and "Whaler" on the skiff.