Revealing mistake: While Doug is driving the IPS truck he stops in traffic, and then Arthur pulls up alongside. Watch the reflection in the truck's side mirror, because we can see crew members pushing Arthur's car as he takes off. (00:19:10)
Revealing mistake: When Carrie holds the paper towels, the kitchen's curtains over the sink are normal, the window is closed and the blinds are down. However, next shot the blinds are up, the double-hung window is oddly open outward sideways, and the curtain is pulled back with a large clamp. Then it's all back to the normal previous way.
Head First - S1-E6
Revealing mistake: When Doug is making breakfast it's clear there is no flame coming from the gas hob. (00:08:15)
Revealing mistake: When they first drive to their class, we see the street lights behind them. When Carrie pulls over to pick up Spence, she turns the steering wheel, but the lights in the back don't turn. (00:07:45)
Revealing mistake: As Carrie skids into the parking spot at the start, skid marks are visible on the floor from previous takes. (00:00:30)
Revealing mistake: When Doug stops to tie his shoe outside the car dealership and Carrie walks up to grab him, you can see the fake back-drop sway with her motion. (00:08:35)
Revealing mistake: When driving the Mini, the reflection on the bonnet never changes despite being on the highway. (00:12:00)
Revealing mistake: Even after receiving the gift basket from the neighbors, the Heffernans are still awakened by their barking dog. When Carrie rushes downstairs Doug stops her at the front door, and the entire left window has been removed (for camera access) from its frame, so there's a large empty hole. (00:13:10)
Court Date - S1-E17
Revealing mistake: When Carrie kicks Doug Spence and Ritchie out the bedroom she shuts the door and the set wall wobbles very noticeably. (00:07:30)
Revealing mistake: When we see the montage of Doug working as a manager, in one overhead shot you can see the image on the PC is simply stuck on to make it seem like it's on. (00:08:50)
Train Wreck - S1-E20
Revealing mistake: Shari from ISP radios Doug about the rush order pickup at 1202 Stratford, so Doug pulls over and soon Carrie pulls him to the back of the truck. Cut to exterior shot of the truck, and the street sign reads "Lafayette, Culver City" which reveals the California location. The truck is parked on Culver Blvd, corner of Lafayette, in front of the well known Washington Building (awnings are now black), which is located a few blocks up from Sony Pictures Studios where King of Queens was filmed. (00:21:35)
Hungry Man - S1-E21
Revealing mistake: When Arthur plugs the blender in you can see the wall move. (00:02:25)
Hungry Man - S1-E21
Revealing mistake: When Deacon drops the suit off to Doug, Doug parks the truck up and Deacon gets in, however the outside of the truck is still moving as if Doug is driving. (00:07:50)
Revealing mistake: Carrie comes into the kitchen, visibly hot and sweaty, and says, "Could it be any hotter?" Doug also has a sweat stain on his back and they stick their heads in the freezer. Suddenly Arthur walks in and says, "Do I have the word pushover on my forehead?" Arthur is wearing a thick shirt tucked into long pants and yet is not sweaty. At his age he would be more visibly drained from the heat than both Carrie and Doug. This happens again later in the episode in the garage.