Plot hole: Joe says that he and Allison told people they conceived Ariel on the weekend of their wedding, even though they knew that Allison was about five weeks pregnant at that time. In episode 6.15 the plot is all about how Allison is expecting Ariel and there is a lot of talk of how she is their first child and they can't tell anyone about it because they aren't married yet. But in the season two episode "Sweet Child O' Mine" it was revealed that they were going to have a baby once before Ariel, a boy they were going to name Brian, but that Allison miscarried.
Continuity mistake: Bridget doesn't seem to be aging as she should. In the first season Joe and Allison talk about their '6 year old' and she doesn't have any friends, Ariel is 9 and Marie is a baby. Rolling on to season 4 - Ariel is 14/15, Bridget is 9 (the episode when she's talking to the credit card guy Mr Reshmi - Joe tells him off for speaking for 10 minutes to a 9 year old). So, my point is - it appears five years have passed - Ariel has gone from 9 to 14/15 and Bridget is 9 - that's only 3 years. Marie was approximately a year old or so in the first season and appears to be 3 or 4 in season 4. It would make sense if Bridget were only 4 in the first season and five years later would be 9 but she's mentioned as being a six year old when the teacher tells Joe and Allison that she doesn't have any friends at school And Then meets Bobby Le Shell. Please correct me if I'm wrong as I'd love to hear an explanation for this.
Other mistake: In the two scenes that occur at Lucky's base in Iraq, it is quite obvious the writers did not do much research about the Army in Iraq now, or the Army in general. Alcohol is not allowed on any US base anywhere in the Middle East during the current conflict, and this is true for all branches of the military. Even if Lucky did manage to procure contraband alcohol, he would not drink it openly, because an MP would arrest him within minutes. If he appeared in his Sergeant's tent drunk, he would be arrested, and severely disciplined, probably demoted. No one on a US base would be known as a habitual drunk, because anyone found drunk more than once would be either sent back to the states for rehab, or dishonorably discharged. Also, in the US Army, Sergeants are never addressed as "Sir." This is one of the very first things a new recruit learns at Basic Training, and it is drilled into him. It is extraordinarily unlikely that a soldier would slip up and call a sergeant "Sir" once, let alone repeatedly, as Lucky's buddy does. After the first time, the Sergeant would correct him.
Continuity mistake: At the beginning of the episode, Van Gogh starts painting blue circles "on" our TV screen (this is the 3D episode). The three circles are big and touch each other. Next shot, seen from a standard point of view, you see him getting back up and the canvas is still on the floor: the circles are smaller and quite far apart.
Factual error: 1-11: I Married a Mind Reader. A nitpicking mistake, but on the set of "I Married a Mind Reader", the front door is a modern steel design. Back in the 60's, front doors were almost always wood (steel doors weren't available until the 1970's or 80's), and the window design would have been larger on a 1960's fan-window wooden door.
Continuity mistake: In Episode 411, "Lady Killen": When Lee Scanlon is in Sensai and the janitor walks him to the kitchen, the doors are push-through doors with no handles on them and with circular windows in them. But when they walk through, the doors are not push-through any more, but have handles on the one side they opened with, and no windows.
Plot hole: It seems strange why Alison and Cynthia Keener don't raise any suspicion with Wheeler's mother after rescuing her daughter Joanna. After Keener finds her and the other missing girl, she says to Alison that the kidnapper had taken them and had been torturing and abusing them for a number of days. However when Alison and Cynthia go to talk with Wheeler's mother about the old kidnapping case (before the two were rescued) the mother states that she has never been kidnapped and had even saw her yesterday. While the mother might not have been aware of her daughter's kidnapping, wouldn't she have been a little perplexed to have found her daughter had been kidnapped and tortured during days she had seen her. Even if this was something that was not shown, why wouldn't Alison and Cynthia (someone who is well trained in kidnappings) find the mother's statement combined with the kidnapping a bit strange.
Revealing mistake: In the first scene of episode 1-15: "Penny for Your Thoughts," the clock shows an impossible configuration. The hour hand is slightly before the five, and the minute hand is between one and two. If it's about seven minutes after the hour, the hour hand should be slightly past one of the other numbers, not slightly before it. (00:00:24)
Continuity mistake: When Allison wakes up from her dream about the murderer, she runs into the kitchen to write down the car's license place on a notepad: 2TH DOC1. However when she holds it up to show Joe, it's smaller written and not across the notepad as she had originally written it.
Other mistake: In the "Silent film" sequence at the beginning of the episode, the D.A. comes in to take the family's home from them. Allison and the kids gather on the bed, and are supposed to be terrified. However, the actress portraying little Marie begins to laugh at one point. (00:01:02)