Character mistake: When Randy Disher is having Chinese food in his apartment with his new girlfriend in 3-12 "Mr. Monk Gets Cabin Fever", he gets a fortune stating that he is going to get money from his uncle, and says that he doesn't have an uncle. In this episode Randy inherits a farm from his uncle who appears to have committed suicide, but was actually murdered.
Factual error: When Monk visits the prison for the first time, he is searched, passed, and has a mini-panic attack because people have touched him. Sharona steps forward to comfort him, and she puts her arms around him. This is a very serious breach of procedure and it is not possible for the guards to miss it, because Sharona has not been searched. It's a common technique for trying to pass contraband called 'a touch through' - a person with an item to be smuggled into the prison (drugs, usually), passes them on to a person who has been searched and is therefore 'clean'. Monk would be taken back to the guard's station to be searched again. He would not be allowed leniency because the guards happen to know or to like him - visitor ingress and egress is always done under CCTV and the guard would know he was being watched - quite possibly by someone who doesn't know who Monk and Sharona are.
Plot hole: The pharmacist's plan is really stupid. He changes all their meds so they don't work, after drinking from the fountain he changed them back so it appears the fountain healed them. The problem is if they think the fountain healed them they're not going to take their meds, so their pain would come back.
Plot hole: Monk wants to take a look at the case that got Christie to leave the force. But given that they are ordinary cops they would not be able to just go and pull internal affairs files.
Revealing mistake: In the scene where Darwin and Monk are in the kitchen and Monk calls Dr. Kroger. Darwin pulls the phone out of the wall, but there is no line from the phone to the jack in the wall.
Plot hole: *Spoilers* Monk and Stottlemeyer cook up an ingenious plan to make Monk appear dead, but how the fugitive Monk acquires his regular clothes (in place of Mitch's uniform), the bullet-proof vest and the gun is not addressed. The police are watching Monk's apartment, Disher is watching Natalie and Julie, and Sheriff Rollins is watching Stottlemeyer, leaving us to wonder just how they managed all this right under their fellow cops' noses. (00:43:00)
Factual error: In this episode, when Sharona and Monk arrive to visit his brother, they talk about the swing set. Monk tells Sharona that his father put up the swing when he was 8 years old but this is a much newer swing set. Look at the curved plastic seats: these have come about in the last six to eight years. It also doesn't look at all rusty like a 40 year old swing would.
Factual error: Since Monk has OCD it would be highly unlikely for him to be on a jury. Plus, Monk works for the police department and since he technically works in the criminal justice system, that would have made him exempt from jury duty.
Continuity mistake: At the end, when Dale Biederbeck is screaming at Monk, Dale is sitting in his wheelchair with both his hands down in his lap. The shot cuts in the middle of his sentence, and suddenly he has one hand up on the cell bars. (00:40:30)
Continuity mistake: Monk leaves his front door standing open in anticipation of his new friend's arrival. No one goes near the front hall, but when Hal gets there, he lets himself in by opening a door that has somehow closed itself. (00:10:30 - 00:11:50)
Continuity mistake: In "Mr. Monk and the Birds and the Bees" Natalie mentions she doesn't have a sister when Julie's "boyfriend" says the aunt hired him to break her and her real boyfriend up. Here she has a sister and a niece.
Continuity mistake: At the start of the episode, when Katherine Rutherford is killed, she lands on her stomach with her eyes wide-open. Yet when Stottlemeyer and Disher arrive and see the cops looking at the body, she is now lying face-up and her eyes are closed. It is hard to believe that the police would move the body that much without first marking its original position with tape.
Factual error: Michael Kenworthy and his robbery crew made plans to move to Ecuador after the heist. That wouldn't work because the United States has extradition agreements with every country in the western hemisphere.
Continuity mistake: In this episode, Randy says that his uncle left him a farm in his will. In the episode "Mr. Monk Gets Cabin Fever", Randy stated that all of his uncles are deceased. Kind of hard to be given a farm from a guy who's been dead since Season 3.
Plot hole: Monk and Natalie temporarily incapacitate Jake before crawling all the way down the hall from the bathroom to the living room while pulling a heavy claw-footed bathtub. Exactly why didn't Monk or Natalie think to consider a more permanent solution to preventing Jake from attempting to kill them again, like grabbing his gun and using it to detain him until the police could arrive to arrest him? (00:30:00 - 00:39:05)
Factual error: When Stottlemeyer and Randy are at the painter's daughter's home they find a picture showing him in front of Carson papers, which leads the Captain to say: they have a contract with the treasury, they are producing the paper for the U.S. currency. This is wrong: the treasury is not in charge of printing the Federal Reserve Notes. Rather it is the privately owned Fed that prints the Federal Reserve Notes and then lends it to the treasury at interest. And the interest added is the reason why there will never be enough money to pay the interest, i.e. the state debt.
Factual error: The hair dryer would not have hurt anyone as it was plugged into a FCI outlet. These outlets will immediately sense the interruption and cut the power to ensure electrical safety. The coach would have been alive. (00:02:23)
Other mistake: The diner Monk enters to eat something after the truck driver gave him five bucks is the same diner that Christie and Sharona are waiting in to meet Monk after work in the episode Monk and the employee of the month. But while this episode is said to be in Wymington, the earlier one is set in San Francisco.
Plot hole: When Monk explains to Miss. Mass how she had murdered Sonny, a flashback of the crime shows that she isn't wearing gloves when she leaves the note to get him to go to the alley. Had the cops checked the note for prints, they would have shown Miss. Mass' fingerprints on it and knew she was responsible for Sonny's death.
Continuity mistake: In the scene where Capt Stottlemeyer is vacuuming Monk's floor, you see the living room has wall-to-wall carpet. But just minutes later when they show the floor again, it is just a throw rug over hardwood floors. The room no longer has wall-to-wall carpet.