Character mistake: When Carrie finds Tina, she mentions the "stuff" that Tina listens to at work, and Tina tells her that it's salsa. We know from previous episodes that Carrie likes salsa dancing, so shouldn't she know salsa music?
Other mistake: On the exterior front shots of the house you see the front door with three vertical windows. But on the interior shots it is just one window.
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)
Visible crew/equipment: Stage lights can be seen reflecting off the fake apples in the table center-piece at the hotel. (00:02:25)
Continuity mistake: In front shots of the house you see that the garage is in the front and opens to the street, but the garage door is behind the house entirely. It seems to open in a back alley or private entrance way. The way it is shown in establishing shots, it can not be open to the front street at the front of the house.
Continuity mistake: The box of Sgt Salty cereal alternates from open to closed between shots when Doug and Carrie are talking. (00:13:30)
Continuity mistake: When Doug, Carrie, Deacon and Kelly are at Coopers, the man in the blue shirt who is talking to the women sitting at the table behind them appears, disappears, walks off and then reappears again during this scene. (00:08:20 - 00:10:40)
Tank Heaven - S6-E21
Visible crew/equipment: When Doug and Carrie close the door after saying bye to the first couple, you can see camera lights and a boom mic moving in and out reflected in the window behind them. (00:06:10)
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)
Continuity mistake: When Deacon and Kirby are at Doug's the house over street is a mid terraced house in one shot, and an end terrace in another. (00:06:00)
Tank Heaven - S6-E21
Continuity mistake: In the scene where Danny has just taken the "nucleus" nacho chip, after Carrie walks in, the chip in Danny's hand keeps changing between shots, then disappears altogether almost instantly and his arms are folded when he begins his next line. (00:02:30 - 00:03:25)
Queasy Rider - S2-E1
Continuity mistake: When Arthur starts telling Doug about when he had a bike, you can see the tv gets switched off. However neither Doug or Arthur turn it off as both of their hands are in screen and the remote is on the table. (00:14:30)
Fixer Upper - S1-E12
Continuity mistake: In "Richie's Song" Doug asks Spence if the M&Ms Spence found under the seat in the car are regular or peanut, Spence answers peanut, and Spence then eats them. In this episode, Spence somehow isn't allergic to peanuts. (00:08:10)
Continuity mistake: In many episodes, scenes are shot on the front porch. It is often shown as a large porch that spans a great deal of the front of the house. But shots of the house exterior from a distance show a small set of stairs with very little space near the door. This isn't a porch on the back of the house as it has been shown to only be door to a small yard.
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)
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)
Window Pain - S5-E2
Visible crew/equipment: When Doug gets into their Jeep after meeting the new neighbours, a man and the backstage can be seen in the passenger side mirror. When the shot cuts back to Doug again it's darker but when he backs up, the reverse lights of the Jeep reveal the man and stage again. (00:26:55)
Queasy Rider - S2-E1
Continuity mistake: When Doug tells Carrie that he is getting rid of the bike, Carrie has got a fag in her hand and her hand is up by her head. Camera cuts and now her arm is down across her lap. (00:15:40)
Continuity mistake: In the scene where Doug's father is shutting off the alarm, he does not enter 2965. We know this is the proper code, because it is Doug's birthday, and it worked when he entered it. It looks like he maybe enters 1459.
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.