Revealing mistake: Right after Ignacio tells Andy and Silas to sit down with him at the diner, it's painfully obvious that the baby that Silas is carrying is a doll.
Revealing mistake: Right after the scene with the witches, Cindy disguises herself while offering coffee to the producer Corky Shimatzu. However, besides the Groucho Marx glasses and nose, she is wearing her normal outfit when a few minutes earlier, she was wearing her witch outfit, had green makeup on her face, and her hair was a completely different style. Then a few minutes later, she goes back to her play costume. That makeup must have taken at least an hour and would take just as long to remove it. Yet she changes from and back to it in a matter of minutes.
Berry Scary - S1-E7
Revealing mistake: Blue is walking down a hall with a paddle ball in his hand. He is twirling around the ball and string around the paddle. However it's obvious that the string is somehow just passing through the paddle itself and not going around it. It's especially noticeable when he stops and the string slows down and visibly passes right through the wood of the paddle.
A Fistful of Paintballs - S2-E23
Revealing mistake: When Chang is getting blasted with the minigun, the safety pads under his shirt are very noticeable. (His shirt is extremely "puffed out" and you can see the outline of pads.) He's been tied up most of the episode and wasn't wearing pads earlier, so there's no way he was able to get pads on in the meantime.
Revealing mistake: The woman becomes possessed while the police are attempting to arrest her. She turns her head around and cracks her shoulders so she can walk at them backwards. They did not change her hand positions, so her right hand is where her left should be and vice versa. (00:11:00)
The Real Man - S1-E6
Revealing mistake: Eileen's cell phone is obviously turned off, as the screen is black when she tries to call Shannon and Jodi.
Revealing mistake: When Alex is talking to Rebecca Pope at the end of the episode, we hear Alex say "Now I know more about you than my friends." Watch Rebecca's left eye on the right if the screen when she says, "That's pathetic." Someone did a bad job of editing the CGI and we see a phantom eye over her left eyebrow.
Revealing mistake: When mini is in the bath at the start of the episode you can see the bandeau she is wearing in the bath when she lays back down in the tub, probably to stop her being exposed.
Aunt Bee's Cruise: Part 1 - S1-E15
Revealing mistake: Aunt Bee is traveling on a cruise ship. The "water" in the background is a painted backdrop which is made all the more obvious by the painted whitecaps.
Revealing mistake: When Matthew is sliding backwards because his shoes are icy, just before he falls you can see the board he was on to allow him to move backwards. (00:02:00)
Revealing mistake: The opening scene was shot twice, complete with a rear-end automobile collision in the foreground for both takes. The initial collision destroyed the taillights of the first car and the headlights of the second car and ruptured the second car's radiator on impact, spilling its contents into the street. The production crew attempted to sweep away the debris with a broom before the scene was reshot. If you examine the roadway before the two cars appear in this scene, you will see a prominent splatter on the pavement that has been swept with a broom almost precisely where the cars impact again moments later.
Revealing mistake: After the car hits Herman, it falls apart. After the left front tire falls off, the prop holding up the frame is plainly visible.
Revealing mistake: When the students see themselves in the TV, (which meant that Skidmore was watching them because Chyna had given her a hidden camera) you can see in the TV that there is actually a green screen on the screen and the video is not actually playing, it was just edited in later.
The Return of the Seven (1) - S2-E1
Revealing mistake: When Dennis is picking up Vicky from the hairdressers in the Jag, you can see people standing around watching the filming.
Blue Wants to Play a Song Game - S1-E14
Revealing mistake: After Blue and Steve play the monkeys jumping on the bed game with the sock monkey, when the mail time song plays Steve gets up excitedly and his arm and hand get cut off.
Dance Dance Revelation - S2-E10
Revealing mistake: When Lily hits Mitchell in the face, her 'arm' is covered by a pyjama-like material, but the next shot shows her wearing a sleeveless dress, showing her 'arm' was really a padded stick.
Revealing mistake: It's obvious by his hand movements that Gunner Graham isn't actually playing the piano.
Suggested correction: If I take some random episodes, S7E5 (01:54) or S3E1 (21:51) or S7E1 (13:21), it's either real or at the very least the touch matches the notes in time. This is all on YouTube for easy check-up. S8E2, which centers on him playing something complicated, doesn't show his hands, so avoids a mistake. Glimpses during opening credits are less well-matched over the seasons, but then, that is supposed to be the score only. Claims that it's all very obviously fake just don't seem to ring true.
Suggested correction: I have recently watched the whole run of the series, every single episode, and I do not agree for two reasons. First, there are no close-up shots of hands on the keyboard. Sometimes it's bound to be a recording, for example when the monsoon breaks and the piano is full of water. But that is not a mistake. Second, the show released its own LP record, and actor John Clegg is credited for playing one musical number on that album. So I'm not so sure if he wasn't the real pianist all along. It makes sense that they'd cast someone who could actually play well enough.
If you look carefully, it obvious to any one who plays the keyboard, he's not playing. Also its as plain as the nose on his face that in shots with him playing the accordion, it's a fake.
Of course the accordion is fake - that is just the one episode where they were sent to the front line, so they needed to do something. But I'd very much like to get an episode & time where it's "plain as the nose on his face" please, apart from special situations like in the pouring rain. (I repeat, no-one else is ever credited for the piano, not even on the record album; and it would be strange casting then, since he was always the mediocre pianist from day 1).
Revealing mistake: In the scene where Mitchell first visits McNair's van, Mitchell's reflection is visible in the window on the left side of the screen during the shot where he first opens the van door. The vampire lore of the show informs the viewer many, many times that vampires (such as Mitchell) and ghosts cannot be seen in reflections, pictures, or videos (their image "cannot be captured"). The reflection can be seen for roughly 20 seconds. (00:23:20)
Kugelblitz - S3-E4
Revealing mistake: At the beginning of the episode, as Sissy is signing the papers under the pseudonym Dana Pocket, she is holding cash in her left hand. The words "pictures" "and "film" can be appreciated on the faces of the bills, revealing this is fake money, often used in Hollywood productions.