Deliberate mistake: Many of the Rangers in the Legendary Battle could not be there since they were portrayed by the same person. All 3 Rockys, all 3 Adams, and both Jasons and Kimberlys were all present.
Deliberate mistake: When the turtles and April escape the building filling up with water, the shot where the hall is filling up with water is used twice.
Deliberate mistake: Probably best for filming the scene, but Jennifer Hart pulls up and parks her car on the street on a red curb in front of an ambulance and walks away. (00:10:12)
Deliberate mistake: When the show premiered on March 18th, 1981 Ralph's last name started out as Hinkley, but after a couple of episodes had aired on TV, on March 30th a man named Hinckley shot then U.S. President Reagan and three other people, so in the remaining episodes of season 1 Ralph's last name was changed to Hanley. His last name was changed back to Hinkley in season 2.
Night of the Sentinels: Part 1 - S1-E1
Deliberate mistake: When the Sentinel is first walking through the mall, its footsteps are so heavy that it shakes the building. When it is shown walking past the shop Gambit is in, there is no shaking of the building, presumably done so Gambit wouldn't notice it. (00:04:08)
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.
Genesis (2) - September 13, 1956 - S1-E2
Deliberate mistake: When Sam ejects and lands on the ground, the closeup is a flipped shot, note the "US Air Force" is backwards on Sam's helmet. (00:19:10)
Episode XCII - S5-E1
Deliberate mistake: Jack stops his motorbike beside a stream, and Jack's weapon strap crosses over his left shoulder when he walks over to have a drink. The problem is when we see Jack's reflection in the water, his image is not reversed; note the strap is still crossing over Jack's left shoulder. (00:07:20)
Deliberate mistake: At Pete's diner, the owner puts the tray down, and instantly glasses appear in front of the 5 patrons. (00:02:50)
Deliberate mistake: While Magnum is with Penelope at the cemetery Magnum spots a man standing by the tree, and when Magnum walks over to stand beside Penelope, this shot is flipped. (00:32:55)
Deliberate mistake: When the sewer worker is trying to escape the Lizard, the fast lanes in both directions of traffic are visibly clear for several blocks, which is extremely unlikely in downtown New York. (00:01:10)
Kill or Cure - S3-E9
Deliberate mistake: In a previous episode the Seals conducted a vehicle interdiction snatch and grab because the HVT they were pursuing was said to have lived in an apartment building with a lot of security, cameras, doorman, etc. Part of the team in Mexico now goes to the HVT's two story house to find her dead. What happened to the building she was residing in? (00:11:00 - 00:12:00)
Deliberate mistake: Throughout the episode, all the police station clocks are still and show the same time (3:33) in different scenes. (00:18:55)
Deliberate mistake: Though the series title is technically inaccurate, since in New York CSIs are called CSUs (crime scene units), it's called "CSI: NY" to tie it in as existing in the same universe as its sister series "CSI: Crime Scene Investigation" and "CSI: Miami."
Deliberate mistake: As usual when the Hulk reverts back into Bruce Banner, he is left wearing nothing but tattered pants. When Mitch McCutcheon sneaks Bruce Banner into the nuclear research facility, Banner is shown wearing his usual outfit of a gray collared shirt tucked into purple slacks that are intact. Given that the Hulk was just in the middle of the Nevada desert, Bruce Banner would be in no position to have a change of clothes on him, and the idea that the top secret facility would have an exact match of his go-to outfit is ludicrous.
The Night of the Tottering Tontine - S2-E16
Deliberate mistake: The knife that has just killed one of the investors doesn't have a trace of blood on it. No one had time to clean it off. (00:20:00)
The Defection of Hawkeye - S1-E8
Deliberate mistake: When Mandarin is watching and wondering why Julia is tailing Clint, the road surface and cliff walls around Julia's car are recycled repeatedly. (00:10:55)
The Stadium - S1-E8
Deliberate mistake: The Korean lady's Mini-Uzi never runs out of ammunition, and she's spraying it at full-auto. A Min-Uzi's cyclic rate is 950 rounds/min. One long squeeze of the trigger and the weapon's dry. Same goes for all the other weapons like the M4 carbines being fired on full-auto, they have the infinity ammo cheat code going here.
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.