Revealing mistake: When Carrie phones Doug at IPS, Doug goes to press the button on the phone for the correct line, but doesn't press any and continues to talk to Carrie. (00:07:40)
The One With Rachel's Date - S8-E5
Revealing mistake: In the scene in the coffee house, Phoebe is talking to Monica who is drinking a cup of coffee. Towards the end of the scene, the camera is on Phoebe who is smiling & laughing at Monica. In the right hand corner is a side view of 'Monica' however, it is not Courtney Cox in the scene, but a completely different actress. [Widescreen version only, although the "wrong" nose is visible in the original]. (00:06:20)
Revealing mistake: While Andy, Aunt Bee, and Opie are at the Hollywood studio watching a scene being filmed, when Andy mistakenly stands up and interrupts the filming we can see the wall and shelves behind the director, and it should look familiar because it's the wall and shelves from Floyd's shop in Mayberry.
The Treaty - S4-E7
Revealing mistake: Tom is talking on the phone in Ron's office. When he turns the phone at an angle the call home screen that has the end button, the speaker button, etc. turns to its side, which means it was a picture - he wasn't actually calling anyone. (00:02:25)
Revealing mistake: Carl, Eddie, and Steve are out ice fishing. At one point Carl falls through the "ice" and you can clearly see that the "ice" is made of some sort of styrofoam. It looks like the stuff used for packaging. The snow looks just as fake.
Subway Wars - S6-E4
Revealing mistake: When Ted uses his laptop to get directions to the restaurant, Bing shows Los Angeles (where it's filmed) as their current location, instead of NY where the show is set. (00:02:15)
Mr. Monk Meets Dale the Whale - S1-E4
Revealing mistake: When Monk is showing how Dale and his Doctor murdered the judge one can see that the knitting of the right chair is already cut to ensure that the policeman will fall through it when he later steps on it.
Revealing mistake: Near the end of the episode, all the castaways are passed out cold when Lord Beasley finally catches his butterfly. Right after saying the line "That's the trouble with you Americans - you simply don't know how to hold your tea" as he's exiting off camera, Mrs. Howell starts to open her eyes slightly, but then quickly shuts them again. Perhaps she thought the cameras stopped rolling.
Revealing mistake: When Shannon walks into the kitchen and gives Stephanie a hug, in one shot of the highchair where Tommy is sitting there is now a doll.
Revealing mistake: During Jack's dance scene, the old lady that he dances with spins away from him and knocks off a man's toupee. The actress was supposed to knock it off as she went by, but it's obvious that she misses and instead quickly reaches over to snatch it off his head instead.
Shoes, Hats, Pickle Jar Lids - S5-E9
Revealing mistake: When Charlie is in the Ferrari, his gets a call from Teddy. When Charlie brings the iPhone to his ear and talks to Teddy, you can see that the iPhone is upside down showing that no one actually called his phone.
Welcome to the Family Part 2 - S2-E25
Revealing mistake: When the family releases Chloe's bubble ability for the last time in the episode the bubble machine is visible.
Revealing mistake: S9 E1 "Bully for Ben": When Ben hits the punch bag sideways, it's easy to tell that someone is controlling the punch bag as it never slows down.
Revealing mistake: When Charles shows the picture of the horse and says "look what you get when you search for 'Charles Boyle medal of valor'" he's typed "peanut butter the horse" into his phone.
Revealing mistake: In this episode Dorothy and Blanche are awakened by a stench coming from the kitchen. After they go to inspect, we see that Rose is making some sort of Krispies treat. As you see her carry the plate to offer Dorothy and Blanch one, you can see that the plate is empty. And once they all start to eat them you can easily see that none of them are actually picking anything up and putting in their mouths.
The Simpsons Christmas Special: Simpsons Roasting on an Open Fire - S1-E1
Revealing mistake: After Homer brings Santa's Little Helper home, Homer and Marge hug, and if you look behind them, the background is upside down. There is a picture hanging upside down, and there is a lamp which seems to be hanging from the ceiling. Then in the next shot, the background is normal. (00:21:40)
The Barbarian Sublimation - S2-E3
Revealing mistake: When Sheldon gets the sword for Penny in the game, Penny walks out and you can see the laptop isn't switched on. (00:07:55)
Gourmet Night (a.k.a. Gourmet's Paradise) - S1-E5
Revealing mistake: When the Colonel first meets Basil, the same shot is used twice of the Colonel twitching.
Revealing mistake: When the mall Santa lands in the Bundys' back yard, everybody looks toward the back, and when Al looks forward, he cracks a smile although he's upset about the matter. Ed O'Neil admitted he couldn't contain his laughter.
Revealing mistake: In "Not Normal" when SpongeBob says "Hmm. This video tape should help," his left arm is missing. (00:01:25)
Suggested correction: Depending on the location settings on his laptop, they could be giving a false reading. My laptop shows I'm in Cardiff Wales while in fact I'm nowhere near.
Ssiscool
The show was actually filmed on a film set in Los Angeles which is probably why the laptop says Los Angeles as the current location. This most probably slipped past the editing crew.