Deliberate mistake: When the world is counting down to the new year, we see people in various countries, Egypt, the USA etc all counting down together. Because of time zone differences this isn't possible. [It is a little joke.] (00:01:35)
Deliberate mistake: In the episode where Mary-Alice Young's house is open for buyer's inspection, the phone number on the "For Sale" sign has been digitally blurred.
Deliberate mistake: About halfway through the show, Roz and Daphne are in the kitchen talking. Daphne pours water into the teapot - but there is no steam coming from the kettle, nor any sound of a boiling/just boiled kettle. No self-respecting Brit would make tea with water that wasn't boiling.
Deliberate mistake: Robert Brown wears a gold turtleneck sweater with his leather outfit throughout the series. Though it's more than 100 years beyond the show's 19th Century setting, he and the producers decided that he looked good in it, so allowed the anachronism to stand.
Wiegel's New Boyfriend - S2-E2
Deliberate mistake: After the credits, the word "Briefing" is spelled "Breifing" in the shot with the caption "Morning Breifing 6:58 A.M." (00:01:15)
Deliberate mistake: These errors I assume were caused by the show running 3 times longer than the real war. Col. Potter arrived at MASH in September 1952 a year before the war ended, then a few months passed by Margaret got engaged for 8 months, then Frank Burns left and Charles took his place. In this time the war would have ended. In the final episode Margaret mentions Charles has been there for 2 years. Which means he would have arrived in 1951 a year before Trapper and Henry left and Col. Potter arrived. It's a lot to take in.
Deliberate mistake: In one of the later episodes of season 2 Turk is seen being bored in surgery and checking the patient's wristwatch to see how long they have been operating. Patients are not allowed to wear jewelry or watches during surgery as there is a VERY high risk of infection and it might kill them.
Smack in the Middle (2) - S1-E2
Deliberate mistake: Ignoring that its very unlikely all of Jill St. John's copious red hair would fit under a wig that passes for Robin's hair, it's impossible that it would emerge from under that wig looking as full and perfectly styled as it does when she's in the Batcave.
Deliberate mistake: In the scene with Brian and Beverly going up the stairs, Brian is in the chairlift, and you can see in front of the wig that Peter Kay wears where the red patch is where he has shaved his real hair.
Deliberate mistake: In Series 1 episode 1 Nick can use a laptop fluently, yet in series 1 episode 2, Nick has to ask where the "." button is.
Deliberate mistake: In the very first episode, the kids are fighting and arguing all throughout the house. Claire then asks Cliff, "Why did we have 4 kids?", referring to Denise, Theo, Rudy, and Vanessa. In all of the following episodes, they actually have 5 kids. I guess they decided to add Sandra (the oldest Huxtable) later down the road.
Deliberate mistake: In the scene where Peter Andre and his producer watch the footage of the royal family, in the background you can see princess Diana and the queen mother who had both unfortunately passed away before Little Britain was made. They had to use the old footage but it is still a mistake.
Strangers on the Shore - S9-E2
Deliberate mistake: When Del, Rodney and Boycie first arrive in France, there is a side view of the white van they are in and it is clear that the driver is definitely not David Jason.
Deliberate mistake: In the shot where we see the cars in front of Victor's (shortly after Victor gets out of the car and gets back in when the traffic starts moving) you can see that after the white car on the right that there are no more cars even though the episode takes place in a traffic queue! If you listen to the commentary on the DVD, writer David Renwick points out the mistake and informs us that they had a limited number of cars for the shot. (00:11:25)
Deliberate mistake: Jesse is looking for his keys and thinks Michelle took them. Near the end, Joey comes home and finds the keys in the door, hands them to Jesse, who puts them in his pocket. A few seconds later Danny comes home, takes Michelle into the kitchen. Joey and Jesse exchange a couple lines and go into the kitchen, where Michelle is sitting in a booster chair at the table. The 3 guys chat for a few minutes, then Jesse is going to leave, but can't find his keys again. It turns out Michelle has them. But how did Michelle get them? She was in the booster seat the entire time Jesse was in the kitchen and Jesse never went to that end of the room, so there's no way she could have gotten them.
Deliberate mistake: When Jill turns off the light to Randy's room, she uses the same switch that Al used to activate the reverse laundry chute.
Deliberate mistake: The circular desk where Carol sits should be rotated 180 degrees so she is facing the elevators. How many times have you gotten off an elevator in a fancy office building only to see the back of the receptionist's head?
Njorl's Saga - S3-E1
Deliberate mistake: Eric Idle's 'Stock Exchange Report' (in Series 3, Show 1) has a very obvious edit in the middle. This is a monologue delivered without cutaways, so the jump in the video tape is very easy to spot. Whether this edit indicates material removed or a simple joining together of two takes is unclear. However, since Idle gets drenched with water at the close of the routine (and given that, under BBC constraints, there was no time for drying out), we can assume that he must have made his fluff quite early on in the piece.