Continuity mistake: When Buffy is talking to Riley, she puts the scarf on her head, on his hand. He talks to her and says "Maybe I am the bad guy," and in the next frame her scarf is back on her head again, then off again in the next frame. (00:24:20)
Other mistake: When Lucy is in the cafe watching the mother and her children, the mother repeats the same dialogue.
Continuity mistake: The age gap between Eric and Cory decreases as the series progresses. At the start of the show, Cory is in 6th grade and Eric is a high school sophomore, meaning they are four years apart, give or take a few months. By season 3, Cory is in 9th grade (confirmed by dialogue mentioning that Shawn, who is in the same grade as Cory, is 15 years old), and Eric is a senior, leading to an age gap of three years. The first episode of season 4 takes place a couple months after the end of season 3, with Eric and Cory returning from a summer Road Trip, but just two episodes later, Cory mentions that he is in 11th grade, while Eric is still barely out of high school, leading to an age gap of two years.
Revealing mistake: (Ep. 4) After Omega takes off his mask and looks in the mirror, when he sees that his physical body doesn't exist he puts his mask back on and screams, but when he shouts, "If I exist only by my will, then my will is to destroy," Omega's mask pops up off his face, and we can see the actor's blackened face as he shouts the last bit of his dialogue. (00:07:10)
Revealing mistake: In the episode where Denise tries on her wedding dress Jim leaves the room to go and wash up. As he opens the door to leave the living room if you look down towards the front door you can see Dave stood by the door frame waiting for the next scene.
Plot hole: Live 50th anniversary episode, aired December 9th 2010 - When Sally is allowed into the rubble to comfort Molly as the firemen attempt to free her, one of them says they'll get Sally a hard hat. When we see her talking to Molly in the rubble, she has no hard hat on and instead one of the firemen is hilariously holding his hand above her head.
House Party - S2-E5
Continuity mistake: Kelly said her youngest brother can burp his whole name Kenneth Leonard Kapowski in one burp. However in the previous year, Kelly had an infant brother named Billy. According to this info, unlikely Kenneth would be younger than Billy.
Suggested correction: Kelly can have more than one brother because in the episode where Kelly gets her job at the Max she said "I cook every night for my 11 siblings". So he could be younger or just have a nickname.
The mistake is valid because she says her "youngest" brother, not "younger." In the episode "The Babysitters" (which was meant to air in season 1 and produced before "House Party"), her brother Billy is an infant and says his first words. Kelly has 6 siblings and she never said she cooked for 11 siblings when getting a job at The Max. She says she sets the dinner table for 9 people three times a night.
Ironically, the show only reveals 5 siblings each in their own individual episode. (#6 is unknown). Bennett (mentioned), Nicki (seen), Kyle (voice heard only), Kenneth (mentioned), Billy (seen) are the 5 of 6 siblings revealed.
Visible crew/equipment: When Dr. DeRaad asks Kerry if she knows Paul Sobriki she tells him to check the board, and as Kerry walks past the door we can see the reflection of a crouched crew member walking backwards, pulling a rolling microphone stand. (00:02:45)
The Séance - S1-E7
Continuity mistake: After Lucy tells Mr. Merriweather that he's invited to the seance, when it cuts to Lucy unfolding the card table legs, note the couch behind her with one normal seat cushion on the left, but in the next wideshot there's an additional shorter cushion under the normal cushion. The small towel also repositions itself neatly on the couch. (00:11:55)
It May Look Like a Walnut! - S2-E20
Character mistake: Rob is having a nightmare, part of which involves the disappearance of his thumbs. When he finds Laura at home, the script calls for him to say, "I want you to help me get my thumbs back," but he actually says, "I want you to help me get my thumb backs." His thumbs are also still there but hidden (you can see a portion of them in one frame of the episode).
The Feminum Mystique: Part 2 - S1-E6
Visible crew/equipment: After the Nazis are defeated on Paradise Island, Queen Hippolyta tells her daughters that she has plans for those Nazis, and at the start of the next shot the set equipment's c-stand is visible at the left side of the screen (widescreen version).
Visible crew/equipment: In the first scene of the episode, a crew member is visible through an open door beside the staircase.
Factual error: A character in the episode has invented denim, but denim was invented in 1873 and was being used widely up to the time period of the series, which is set in 1893.
Suggested correction: The entire series was set in an alternate history of sorts, so most, if not all, historical "inaccuracies" cannot be regarded as mistakes.
The Suitcase - S4-E7
Factual error: At the beginning of the episode, the male employees are all discussing James Bond. It is mentioned that 'James Bond goes underwater, he met a girl underwater'. This refers to the plot of the movie 'Thunderball' (it does not occur in the Thunderball novel, nor any novel or film prior to this). The main plot of this episode centres around the Sonny Liston VS Cassius Clay fight in May 1965, and 'Thunderball' was not released until December of that year.
Revealing mistake: Any time any character is driving a Suburban, or any other vehicle with a column mounted shift lever, the shifter is in park while they appear to be driving.
Visible crew/equipment: When Kim is talking to Joan the security guard, a crew member drinking a cup of coffee can be seen in the dojo.
Factual error: In scenes from the oil rig there are shots that show the shore line. This oil rig is supposed to be offshore of Louisiana. However, mountains can be seen in the shots of the shoreline. There are no mountains in Louisiana.
Continuity mistake: Ruth is seen in a flashback. The young Ruth has a mole on the left side of her face, as does the adult Ruth. But in one shot, when she is slapped by her father, the mole appears on the right side. (00:20:00)
Continuity mistake: On the video of Ian supposedly killing Alison, we see her arm fall to the ground with her "Alison" bracelet visible. But in a later scene where Emily watches Ian put his bag in the athletics room, we cut back to the video and Alison's arm suddenly has a sleeve covering up her bracelet. When we see the video again later in the series, her bracelet is visible again.
Factual error: Calleigh Duquesne frequently wears completely inappropriate clothing throughout the whole series. She often wears blouses that are so low cut that the neckline is below the lower curve of her breasts. No officer of the court in the US would be allowed to dress this way. There is no grey area here, and this is not a character mistake - first time a CSI turned up at work dressed like that, she'd be sent home to change. Second time, she'd be on suspension until she agreed to change her dress standards. Also (and this regularly happens in CSI: NY as well) she is regularly wearing high heels - also a certain no-no for as CSI. Incidentally, male CSIs have equally strict dress standards.