Deliberate mistake: Richie was an infant in season one, and beginning with this season, he has been aged up to at least 3 years old while none of the other characters have aged up.
Deliberate mistake: In the butter skating scene, the boys signing Paisley's cast are not writing anything. They are just pretending and their pens don't even touch her cast.
Jeannie, the Hip Hippie - S3-E6
Deliberate mistake: Phil Spector is credited as having played "Steve Davis", but that name is never used in the episode; he is instead addressed by his real name.
Log 1: The Impossible Mission - S1-E1
Deliberate mistake: Halfway through the episode, they are chasing car thieves in a drainage channel. The thief's car comes to the end of the road and crashes into a deeper gully. You can see that the windshield has been taken out of the car, although it was previously there. They cut away and when they come back, parts of the windshield are back in the car, but the whole center is missing.
The Trouble With Mr. Bean - S1-E8
Deliberate mistake: When Bean is putting on his socks as he is driving, his foot presses the horn in the centre of the steering wheel. Except that the horn control is actually on the right-hand column stalk (you can see the horn symbol on it). This was most likely an added comical sound effect.
Deliberate mistake: When Fluttershy is telling off the cockatrice, her back legs and her wings turn to stone. But when she gives it the stare and the camera is right in her face her wings are outstretched.
Deliberate mistake: Although it was done for plot purposes, no school photographer would only take just one shot of a class photo. They generally take up to 15 to 20, as it is difficult to get everyone to look at the camera and smile at once (and hopefully not pull silly faces).
Deliberate mistake: After it is revealed Won-hyung has taken over Yeom's body, he is shown walking alone on the street and says aloud "She's not afraid of going to Hell? I can't make it so easy for her. Will she be able to leave behind the person she's been pining for so easily? I can't wait to watch the heart-rending sight." There is no reason for him to say this out loud. He is alone and not talking to anyone. The only reason he is saying this is so that the audience knows his plan. (00:33:23)
Deliberate mistake: Inside the home that has been infested with Evil, the state police confront a possessed girl who attacks them. After some futile gunfire, the possessed girl is still standing. The female officer goes for her backup gun, which for some reason is a small over-and-under Derringer (meaning she has two shots maximum). She ends up firing the Derringer five times in just a few seconds, with explosive damage and without reloading. Director Sam Raimi probably staged the 5 gunshots on purpose, knowing that a two-round Derringer was a ridiculously-limited piece of firepower. Raimi probably did this as a tongue-in-cheek tribute to Ash's bottomless double-barrelled shotgun from Evil Dead 2 and Army of Darkness.
The High Life / Best Friends - S2-E10
Deliberate mistake: In "The High Life", there is a scene where Stinky submerges his head in a tank of water. He delivers the line, "Gee willickers, it's still ticking", and everyone somehow understands what he is saying with his head underwater.
Suggested correction: Nobody responds to what Stinky says, so there's no reason to assume that everyone understood him.
The Hit Car - S1-E3
Deliberate mistake: When Starlet asks Ralph if he believes that stars can predict his future, Bill tells them to put a dimmer on the googoo eyes because of the killers on their tails, and the two shots facing Bill are flipped. (00:14:40)
Thank You and Good Night - S1-E8
Deliberate mistake: In the Maisels' 1954 wedding reception flashback, Midge hired professional dancers who perform the "Bottle Dance" (where they slide on their knees). This famous dance, often performed at Jewish weddings and social events, was choreographed by Jerome Robbins for "Fiddler on the Roof," which debuted on Broadway in 1964. It did not exist in 1954 but, as an inside joke, while Midge watches, she says, "That's really good. They should do something with that."
Better than Average Cory - S6-E5
Deliberate mistake: When Rachel is choking and writes down "I'm choking to death" on the paper on the counter so Jack will help her, you can see she is just scribbling the pen across the paper and not actually writing anything. (00:06:36)
Wizards vs. Vampires on Waverly Place - S2-E26
Deliberate mistake: Justin tells his dad he will write the idea on the white board (the theme in the restaurant/add more of an experience) yet he just scribbles, and in the scenes where you see a bit behind him, the whiteboard has scribbles instead of words where he was supposed to write.
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.
Formidable Enemy!? Mother Coordinator Enters! - S7-E37
Deliberate mistake: This Pokémon Trainer's Choice segment incorrectly claims that Arbok evolves into Seviper, which isn't true. (00:11:38)
Intermediate Documentary Filmmaking - S2-E16
Deliberate mistake: This episode is meant to be entirely a documentary made by Abed. At the end of the episode, there's a shot where the gang is looking into Pierce's window, except the camera is right in front of the window they're looking through. If Abed was filming this he would literally be right in front of the gang, completely obscuring their view through it.
Deliberate mistake: Why would Al have his Polk High football uniform in England?
Suggested correction: Al cherishes his memories as a high school football player. It's quite possible that he takes the uniform with him on some trips, especially when going to another country. I've known people who do this with items that are important to them; i.e. a jewellery box or a favourite picture of family. They feel better keeping the item with them, in case something happens at home while they are away.
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 ghosts often walk around furniture even though it was established that they can walk through solid objects.
Suggested correction: Just because they can walk through solid objects doesn't mean they have to. They were used to walking around things in life so just carry on doing so as a reflex action. They often use open doors too, only walking through walls when it's more convenient for them to do so or the doors are closed.