Mr. Monk Meets His Dad - S5-E9
Deliberate mistake: In the opening scene, Wood's tie is grabbed by an exposed fan belt located above the side of the engine. However, this belt/pulley assembly doesn't exist in a real truck's engine compartment - the fan belts are all in front of the engine, where the camera can't see them easily. The prop master must have added this dangerous device to the truck to allow the camera to see the strangulation.
Deliberate mistake: Every time the investigators deal with IP-addresses, the addresses on display are impossible. Each of the four parts of an IP-address has to be between 0 and 255. As they do have to use IP-addresses some time, they could use addresses starting with 10. Those would be real addresses although not used as an official IP-address. This isn't the same as phone numbers using 555 - any IP address over 255 just wouldn't work. It would be like mentioning a phone number which uses the symbol for pi.
Day 2: 6:00 P.M.-7:00 P.M. - S2-E11
Deliberate mistake: When Jack and that FBI team are looking for Sied Ali in the mosque, Jack finds a burning body in another room. He is led to believe that it is Ali, because the body's clothes matched the description that Kate Warner had given him. It is obvious that the skin is badly burnt, yet the clothes are barely scorched.
Slammin' Sammy's Stunt Show Spectacular - S1-E5
Deliberate mistake: Watch the end of the test run for Michael and KITT. Michael was using the KITT steering wheel, but then he gets out of the car and it switches to a performance steering wheel instead.
Deliberate mistake: 9-12 "The Bells Toll at Noon": When McGarrett picks up Danny and drives away in his Mercury Grand Marquis, the rear view mirror is missing, probably removed to prevent it from blocking the actors' faces. It reappears later on. (00:33:00)
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)
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.
Cold Stones - S6-E11
Deliberate mistake: Tony smashes AJ's front windshield of his Nissan SUV one time with a plastic sports helmet and it leaves a hole 4 times the size. Not only is the scale size of helmet to hole incorrect, but front vehicle windshields don't shatter like that. Modern windshields are made of laminated safety glass, which consists of two curved sheets of glass with a plastic layer laminated between them for safety, and bonded into the window frame. It would've taken many impacts to cause such a hole, not one hit. (00:49:00 - 00:49:45)
Mr. Garrity and the Graves - S5-E32
Deliberate mistake: Garrity blackmails the town citizens into paying him not to resurrect their unlamented "loved ones." Amazingly, every man in the saloon just happens to have hundreds of dollars ($500 - $1200 each) in his pocket to pay up with. In 1890 money, that's roughly equivalent to a group of modern-day bar patrons all carrying ten to thirty thousand dollars around in their pockets. The scenario was apparently used in spite of its incredibility just to more quickly advance the plot.
Yankee White - S1-E1
Deliberate mistake: Fornell doesn't recognize Gibbs, but subsequent episodes establish they have a long history together.
Second City - S1-E12
Deliberate mistake: Kermani finds a nitroglycerin tablet in the suspect's apartment. Because we need to see it when he holds it for the close-up, the tablet he has is much too large to be nitro. That drug is dispensed as an extremely tiny pill designed to dissolve instantly under the tongue. (00:22:30)
Deliberate mistake: Beth shoots Bryce three times in the chest, and he falls face down on the floor. She then drags his body across the floor, also face down, to in front of the sliding door, but there is no sign of blood anywhere.
Deliberate mistake: When James is shot on the courthouse steps, the crowd of reporters that has gathered quickly scatters to escape the gunfire. One of them is a woman in a black windbreaker holding a camera. The camera cuts away briefly and then back to the crowd - you see the exact same people, including the woman in black running in the exact opposite direction as before. The footage was apparently mirrored and repeated for the second shot of the fleeing crowd.
Deliberate mistake: When the investigators are in the basement wine cellar, they turn on their flashlights to illuminate the pitch black area as they walk around. However there is a light source moving with the camera shining on them as they are casting a shadow behind them.
Deliberate mistake: "Treasure of the Ages": Darien delivers Mary's child during the hurricane. There's no time lapse in the scene, but somehow the kid emerges perfectly clean: no blood, no placenta - and no umbilical cord. Darien also neglects to wash his hands before reaching in to turn the breeched baby around. (Ewwwwww!) (00:45:00)
Crisis on Earth-X, Part 2 - S6-E8
Deliberate mistake: During the big battle, Arrow is knocked down and when he opens his eyes, the reflection in his eyes is tilted over to give the sense he's seeing things sideways. But the reflection should still have shown the proper orientation no matter what orientation his eye was at. Think of looking into a mirror and then rotating the mirror to the side, the reflection wouldn't rotate.
Perennials - S8-E11
Deliberate mistake: In the outside shot of the unsub's motel in Pensacola, Florida, the sky is black as if someone behind the scenes tried to digitally remove part of the background in post, but did a really bad job.
The Hounds of Baskerville - S2-E2
Deliberate mistake: The army major wears a full beard. British Army personnel may not wear beards. (The beard is a nod to the original canon character on which he's based, John Barrymore, who is described in the book multiple times as being a "black-bearded man").