Continuity mistake: Monk and Natalie question the landlady, Sylvia, about the missing guest. Every time the camera angle changes, Sylvia's arms change from being crossed in front of her to hanging loosely at her sides.
Mr. Monk and Little Monk - S4-E8
Continuity mistake: When the kids are standing in front of the lockers, one of them is holding Monk's clarinet. The position of the instrument in his hand keeps changing between shots, from bell-up to bell-down, then bell-up again.
Mr. Monk Goes to the Dentist - S4-E15
Continuity mistake: When Randy is at Monk's place talking about hiring him, Monk says "Like who?" to which Randy replies "Like Me". While Randy says this he is holding a glass with one hand, the other being in his pocket. In the next shot, when Natalie says "Is it about the dentist?", Randy is holding it with two hands. Then, in the next shot, he is holding it with one hand again.
Mr. Monk and the Astronaut - S4-E14
Plot hole: The murderer mails a garage door opener with the button taped down to his victim and kills her by remote. But A) With the switch continuously in the "on" position, the battery would die long before the package arrived, and B) Door openers use special frequency tones that are set much like a safe combination. The likelihood of one control opening 3 different doors in the same area, as it does here, is virtually nil. (00:33:30)
Mr. Monk and Mrs. Monk - S4-E6
Continuity mistake: When the Trudy impersonator is talking to Janice's father in the diner, the venetian blinds on the window to his left alternate between raised and lowered positions as the shots change. (00:06:50)
Mr. Monk Gets Jury Duty - S4-E16
Continuity mistake: When the man with the letter from the Attorney General is telling Stottlemeyer not to 'screw it up', he is moving the letter in his hand. However, every time we see Stottlemeyer front on, there is a corner of the letter in the shot, and the letter remains stationary even while the other agent is moving it.
Mr. Monk and the Other Detective - S4-E1
Continuity mistake: During Monk's therapy session, Dr. Kroger places his black folder on the arm of his chair. Every time the camera angle changes, the position of his right arm shifts from resting in his lap to lying on top of the folder.
Mr. Monk Gets Jury Duty - S4-E16
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.
Suggested correction: First, he would have to ask for exemption in writing prior to serving, with proof, regarding hardship for his OCD. While it's possible his doctor might say serving jury duty would result in physical harm due to his mental illness, it's unlikely to be given by Dr. Kroger. And Monk is not an active peace officer, so that wouldn't earn him an exception.
Mr. Monk Goes to the Office - S4-E4
Continuity mistake: When Monk and Natalie are talking to Kemp in his office, the desk ornament and the cup of pencils that Monk keeps organizing change positions between shots. In the shots from Monk's side of the desk, the ornament is closer to the door. In the shots from Kemp's side, the pencil cup is closer. (00:09:40 - 00:11:20)
Mr. Monk Goes to the Office - S4-E4
Continuity mistake: When Monk is trying to join the two cops' conversation about football, in the shots from the side of the police car that they're standing near, the two cops are standing less than a foot apart. In the shots from the other side of the car, they're far apart enough for Monk, Natalie, and Captain Stottlemeyer to stand between them. (00:03:00 - 00:05:00)
Mr. Monk Gets Jury Duty - S4-E16
Continuity mistake: In the jury room, the two windows behind Monk have venetian blinds, which are raised halfway on the right window. But in several shots of the science teacher coming over to identify the white powder, the right window's blinds are pulled down. (00:35:00)
Mr. Monk and the Astronaut - S4-E14
Continuity mistake: When Steve Wagner gives the class red laser pointers, he tells them to pass them back. The girl on the far right of the shot turns around. When the shot changes, she begins to turn around again.
Other mistake: During the flashback of the perpetrator beating up the victim with a baseball bat, the shot is visibly spliced and there's a jump cut while he is between swings of the bat. (00:32:50)
Mr. Monk Bumps His Head - S4-E11
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.
Suggested correction: This is trivia at best. While the set may be reused, it's not meant to be the same diner. It might be a chain restaurant so they look similar, but the seats inside are different.
Mr. Monk Gets Jury Duty - S4-E16
Factual error: When Natalie hears the jury's muffled screams inside the locked room she uses the fire extinguisher to tear off the door knob. But a locked door without a knob is actually only harder to open, because like that you cannot turn the mechanism even if it was unlocked.
Mr. Monk and the Secret Santa - S4-E9
Continuity mistake: In the beginning scene it shows someone injecting a liquid, with ease, into what appears to be a corked wine bottle. Then around the 13-min mark you see the Captain re-gift the bottle and when the person opens it, it's a pull cork with a hard top, something a needle would not easily go through. (00:00:10 - 00:13:23)
Mr. Monk Goes to the Dentist - S4-E15
Character mistake: He extracted the wrong tooth. He states 3 is the problem, then goes to the other side (left), which would be tooth 14.
Continuity mistake: After DeLancy loosens the tie Stottlemeyer gave him, the position of the knot changes without him touching it.
Mr. Monk and Little Monk - S4-E8
Continuity mistake: After the principal takes the stolen money, he shows the $5 bill he wrote on. But in the close up, the bill changes and so do the way the fingers are positioned.
Mr. Monk and Mrs. Monk - S4-E6
Continuity mistake: When "Trudy" walks into the coffee shop, Natalie flips the picture over onto the counter. In the next shot, she's holding it against her body. It's back on the counter the next shot.