Continuity mistake: There is a shot where Randy is trying to cross the police tape and an officer stops him, and he can be seen briefly arguing. However, when it cuts to the next shot, we see that argument happening again in the background, repeated. (00:07:20)
Continuity mistake: In the scene where the two guys are playing chess, the guy with the black hat knocks over the chess pieces after losing. He then starts scrambling up the pieces and leaving his hands near the chess board. When the shot changes to a wide shot of Monk walking away the guy suddenly has his hands on his head.
Continuity mistake: When Monk is lost in the street crowd after getting pushed into the subway car, his left shirt collar is sticking up over his coat. It's still up when he puts his hands to his head, but is tucked neatly back in in the next shot, though he still has both hands on his head. A few seconds later, it's the right collar flap that's sticking out instead.
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.
Continuity mistake: Darwin the chimp pulls a large blue bowl from Monk's kitchen cupboard and throws it on the floor, breaking it. We cut to a close-up of Darwin spinning, then pull back as he starts pulling out glasses - and the blue bowl is back on the shelf, intact. When the angry landlord enters, Darwin pulls the same bowl from a different shelf and throws it again.
Deliberate mistake: All the dishes that are usually neatly arranged in Monk's kitchen cupboards (pots, pans, stacks of plates etc.) have been replaced here by cheap plastic ware, so that Darwin the chimp can pull them all out and throw them. Though we hear shattering-glass sound effects as they supposedly hit the floor, the dishes Darwin bangs together and throws are very obviously plastic.
Factual error: The cops gain entry to the panic room to be faced with a chimp waving around a loaded handgun, apparently having shot a man, and shrug and make jokes about reading him his rights, instead of expressing the slightest concern that this animal might shoot them. Cops shoot remotely aggressive dogs all the time, but an ape with a gun doesn't even make them raise an eyebrow. Plus the police never did a gunshot residue test on the chimp. Standard procedure, and would've proven they didn't shoot.