Mr. Monk and the Daredevil - S6-E7
Revealing mistake: When Monk, Natalie, and Joey are fighting on the roof, the end of the metal pipe in Joey's hand wobbles around a lot, as if the pipe is made of rubber. (00:37:20)
Mr. Monk and the Daredevil - S6-E7
Revealing mistake: Watch as Natalie fights with Harold's cousin on the roof. The same shot where she's barefoot, she's also got thicker hair, indicating a wig on a stunt double.
Mr. Monk and the Wrong Man - S6-E8
Revealing mistake: During the fight between Max and Paulie, the stunt double for Paulie is easy to spot - he has a full head of dark hair, whereas Paulie is gray and largely bald on top. (00:23:30)
Mr. Monk Joins a Cult - S6-E11
Revealing mistake: When Monk and Natalie are talking to the cult members, a Culver City bus can be seen driving in the background, which is a Los Angeles bus, but the show takes place in San Francisco. Culver City is home to a lot of movie shooting. (00:09:15)
Mr. Monk Is on the Run (2) - S6-E16
Revealing mistake: When Natalie visits Dale in prison you can tell that Dale is wearing a "fat suit". The suit on his arm is folding up on itself like a glove.
Answer: Notice also that in the opening credits scene when he is touching parking meters her also wipes his hand on his clothes each time he does it.