Other mistake: Doug says in 4-11 "Repo Man" that he doesn't know when Carrie is in bed or not. However in this episode he states that he can't sleep unless someone is next to him. (00:01:10)
Continuity mistake: When Carrie is starting her new work position, her bag on the desk behind her moves without anyone touching it. (00:04:20)
Window Pain - S5-E2
Continuity mistake: When Carrie and Doug are having the discussion about the dry cleaning, the way Carrie is holding it changes instantly. (00:06:10)
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)
Window Pain - S5-E2
Revealing mistake: When Arthur jumps over the turnstile at the subway where Spence works you can see it is a stuntman wearing the same outfit as Arthur. (00:37:15)
Window Pain - S5-E2
Continuity mistake: When Doug and Carrie are arguing outside the neighbour's house, Doug takes a big swig from the Scotch bottle and then puts it on the ground. After the police pull up, the shot cuts back to Doug and Carrie. Doug picks up the bottle from the neighbour's porch railing. (00:42:45)
Continuity mistake: When Carrie starts praying in the bedroom, Doug has his hands together. Camera changes and he has got his watch in his hands. A watch that was not in his hands or on his wrist before, might I add. (00:09:50)
Continuity mistake: In the middle of the night when Carrie finds Doug rolling the ham-n-swiss doobie in the kitchen, he dips it in the mayo, and when the shot changes, there's no mayo on it and he dips it again, then takes a bite. (01:25:00)
Mammary Lane - S5-E5
Continuity mistake: At the beginning of the episode, the establishing shot shows a bowling alley with a sign that reads Mar Lin Do Lanes. A few minutes later, Doug welcomes Denise on behalf of the family at Bowl-O-Rama. (00:04:10)
Mammary Lane - S5-E5
Visible crew/equipment: When Denise is running away and Doug is on the floor, a camera shadow is very clear on Denise's car. (00:21:30)
Revealing mistake: In the final scene of the episode, Arthur is searching for used bottles of nasal spray. He empties the contents of the trash can on the kitchen floor and finds one after sifting through the trash. However, the bottle had already been positioned on the floor next to the trash can before he picked up the trash can so it would be easy to find when the trash was emptied on the floor.
Revealing mistake: When Carrie knocks the cards over at the start, some stay in the pyramid shape despite being knocked over, revealing the cards are glued together. (00:03:15)
Continuity mistake: When the IPS guys are discussing the Superbowl party, one of them takes a drink. He then lowers his can. When the angle changes, the can has changed hands. (00:04:20)
Continuity mistake: When discussing the Superbowl at IPS, Danny has a roll in his hands. Camera changes and he picks it up again. (00:04:30)
Visible crew/equipment: Just as Arthur walks in on a mobile phone, a boom mic is visible at the top of the screen. (00:04:00)
Continuity mistake: When Carrie takes the first lot of Hofferman's pictures off Doug, she's holding them portrait. Camera cuts and she's holding them landscape. (00:05:30)
Revealing mistake: When Deacon tries the doors on the van, the wall moves, revealing it's not a van but a set. (00:08:30)
Continuity mistake: The leaflet in Carrie's hand at the start vanishes instantly. (00:03:10)
Continuity mistake: When Carrie is on about having never spent that much on a vacation, she has a leaflet in her hand that is open. Camera cuts and now it is partially closed. (00:03:10)
Visible crew/equipment: When Carrie asks Doug to go and check out the smell in the basement, there are tape markers visible by the fridge. (00:05:20)
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.