Continuity mistake: When Doug sits down to read his book, he has his book on his tray. This then disappears as the shot changes. (00:11:20)
Ssiscool
Continuity mistake: In the scene where Arthur is on the phone with PBS to complain about getting a "Civil War Series" box set, the actual set of tapes changes drastically. When it's on the table and when Carrie brings it over to the counter its a pretty large, has an American flag motif, and says "Civil War" across the top. When it cuts back to it sitting on the counter its a much smaller box with a plain design and says "The Great War" along the bottom. It's obviously a different set, not just the camera angle. (00:14:40)
Queasy Rider - S2-E1
Visible crew/equipment: When Doug comes into the garage and falls over for the first time, a tape marker is visible on the floor. (00:07:05)
Ssiscool 
Visible crew/equipment: Near the beginning when Doug comes into the kitchen and smashes the cake with the watermelon, you can see a stage light reflecting in the door window 3 times as it swings open. (00:00:10)
The Minister
Continuity mistake: When we first see the front of the house there is no wall. When we see Doug for the first time, outside the door is a wall. (00:00:05)
Ssiscool 
No Orleans - S4-E16
Continuity mistake: Doug made a blue snowcone in the kitchen and then goes into the living room to talk to Arthur. When he crosses the door in to the living room, the initially full snow cone is now almost gone. (00:02:05)
Visible crew/equipment: When Doug opens the car door at the very start, a boom mic is reflected in the window. (00:00:20)
Ssiscool 
Continuity mistake: Arthur and Doug are sitting with beers in the basement. Arthur doesn't open his beer, but the sound of a bottle opening can be heard and suddenly his beer has foam all the way up to the top of the bottle. Arthur stands up and the bottle is still unopened. It cuts to Doug, then back to Arthur with no beer at all. Again it cuts to Doug, then back to Arthur, and he is holding the unopened beer again. (00:18:30)
BradDibs
Soft Touch - S2-E22
Continuity mistake: At the beginning, when Carrie is trying to park the car she's wearing a 3/4 sleeve blue top in the closeups, but in the overhead shots of the car the driver is not wearing that blue top.
stephenbeattie
Continuity mistake: At the store, Doug picks up 5 or 6 bags of sweets. Most noticeable is 2 yellow bags. Camera cuts and they have disappeared. (00:01:05)
Ssiscool 
Continuity mistake: When Doug first enters the gym, you can see a price tag hanging off of the front of his weight belt. In the shots following this, the price tag is gone. (00:11:10)
Roxy
Visible crew/equipment: When Doug is getting a lift from the Priority Plus driver after being rescued from being stuck in the drive-thru, you can see the camera truck (the truck they use to film exterior road/driving shots) in the reflections of the glass windows of buildings behind Doug when the camera cuts to him.
Buskieboy
Continuity mistake: In the overhead shot when Carrie parks there is no-one around. From the internal shot, there are 2 people visible through the side windows. (00:00:40)
Ssiscool 
Continuity mistake: When Carrie asks Arthur how a legless dummy will protect her on the subway, her arms are either on the table or off, depending on the shot. (00:10:30)
Ssiscool 
Continuity mistake: At the start Doug puts a drink down after taking the top off. Camera cuts and the lid is back on. (00:03:30)
Ssiscool 
Continuity mistake: When Doug goes to meet up with Ray, Richie zips up his jacket. In the next shot his jacket is unzipped. (00:06:20)
Mortug
Strike Out - S3-E7
Continuity mistake: When Arthur sits down for his meal, there is a bottle on the table. The lid is either on or off depending on the shot. (00:03:45)
Ssiscool 
Strike One - S3-E5
Visible crew/equipment: When Spence's taxi pulls away, a crew member, light screen and stage light can be seen reflected on the window of the taxi. (00:18:10)
Ssiscool 
Dire Strayts - S2-E8
Continuity mistake: When Doug is talking to Ray at the table, the position of his beer changes between shots. Watch the label. (00:02:45)
Ssiscool 
Dire Strayts - S2-E8
Continuity mistake: When Doug talks about grown men not being able to watch the game, the amount of head on his beer changes instantly. (00:02:40)
Ssiscool 
Answer: Sara hasn't been mentioned in later episodes, and it suggested in later episodes that she never existed, and that Carrie is an only child. Kevin James stated that the producers couldn't think of an good plots to use with Sara, so they left her out.