Revealing mistake: Any time a laser is fired in the show, there are no scorch marks on the walls where they hit.
Visible crew/equipment: When Max and 99 are trapped in the room with the hatch that leads down to the Guru's chamber, the filmmakers didn't bother to make it seem like a giant hole in the ground, and they also didn't bother about the floor of the set being about ten centimetres below the hatch.
Continuity mistake: When anybody dives into the lake, their wetsuits are black. But in the water, they are grey.
Plot hole: Zharko's process of using the dead bodies of agents and reviving them could only work if he had them at about at most a day after they were killed. Since his secret lab is on a deserted island in the middle of nowhere, they could not have got the bodies to him in time. The Chief also said that the bodies suffered severe damage, so their ability to move would be seriously hindered, but they work fine.
Closely Watched Planes - S4-E3
Factual error: If there really was a hatch leading into mid-air in the airplane bathroom, instead of being soundless like shown, it would be incredibly loud and Max would have noticed. Also, the sudden pressure change would have sucked him out no matter what he did to stop it.
Character mistake: The leader of the Purple Knights says that they would only be bike riders if they couldn't tell which gender someone was by their hair. This is a major mistake, because if you look at the hair of the Purple Knights, it's incredibly easy to tell which gender someone is.
Revealing mistake: When Hymie does the high jump, when the film cuts to a shot of him clearing the bar, Hymie's hair is curly when it should be flattened down like when he took of and as he landed. It is obviously a stunt double.
Audio problem: Max is firing a weapon on the garbage scow when his gun suddenly stops. He exclaims "It's jammed!", but his lips don't move. Also, what is he firing at? There's nobody there.
Plot hole: The scheme to lead a blindfolded Max and 99 to what they think is the airport via an illusion room would not work the way they do it. Since the base is underground, there is no way that what they did to represent ascending to ground level that would make a person think they were above ground.
To Sire, with Love: Part 2 - S4-E21
Revealing mistake: When the tarantula is released into the room, the spider is a plastic model in its container when it's on Max's shoulder, and when they kill it with the horseradish.
Witness for the Persecution - S3-E3
Plot hole: In this episode, the villain makes a phone call to KAOS headquarters when he's captured demanding that they kill Max to stop him testifying in court against him. Later, several say that Max is the only witness to the villain's crimes, but the Chief and 99 were in the room when the villain made the call, so they could have been witnesses to "conspiracy to commit murder."
The Little Black Book: Part 1 - S3-E16
Audio problem: When Max is fighting the waiter, several times he misses the waiter completely, but you can still hear the sound.
Revealing mistake: At the start, when Max falls off his police motor cycle, he is obviously a stunt double.
Visible crew/equipment: Lights are reflected in the aide's glasses when Max and 99 are talking to him on the ground.
Revealing mistake: When the Prime Minister's aide falls out of the car, he is a dummy.
Audio problem: During the joust scene, Max turns around to have another charge at the Knight and the crowd is clapping, but there's no sound at all.
Continuity mistake: During the joust scene, several tyre marks on the ground from the motorcycles disappear from the ground.
Other mistake: The same shot of Max charging on his motorcycle is used twice in less than a minute.
Revealing mistake: During the fight scene in the gymnasium, Max is a blatant stunt double in some shots.