Visible crew/equipment: When Carrie notices that Doug has walked out the room, there are some tape markers on the floor from where Doug was stood. (00:09:40)
Continuity mistake: When Carrie say to Doug that they are sleeping on the fold out couch, her arm goes from on her hip to hanging by her side instantly. (00:11:00)
Continuity mistake: Carrie cuts Kirby's burger in half with a knife in her right hand. Camera cuts and a fork has appeared in her left hand. (00:10:30)
Continuity mistake: When Carrie is serving up the burgers for dinner, she places one on Kirby's plate. Camera cuts to Kirby sitting down and the burger has vanished. (00:10:25)
Strike One - S3-E5
Visible crew/equipment: When Carrie is trying to return the truck, there are tape markers visible on the floor. They are little white dots. (00:11:35)
Strike One - S3-E5
Continuity mistake: When in the garage, the way Carrie's arms are crossed changes instantly. (00:09:50)
Visible crew/equipment: When the dummy is on the sofa with Arthur, the stage lights are reflected in its sunglasses. (00:16:00)
Continuity mistake: When Doug and Carrie are in the bedroom discussing the health benefits of Doug losing weight, Carrie's arm is constantly switching from in her lap to on her head. (00:06:50)
Visible crew/equipment: When Arthur is saying about how someone should be able to go out their house and turn left or right, he looks up and the top of the set and the set lights are visible in his glasses. (00:02:45)
Continuity mistake: The first time Doug throws a ball at the bottles, we see one bottle remain lay down on the stand. Camera cuts and this bottle has disappeared. (00:18:00)
Continuity mistake: The guy on the stall puts 3 balls down in front of Doug in a line. Doug picks up the ball furthest from the guy. Camera cuts and now Doug has the ball closest to the guy. (00:17:30)
Soft Touch - S2-E22
Visible crew/equipment: When Doug and Carrie go to get up from having dinner with Saskies, tape markers are visible on the floor by their chairs. (00:05:30)
Frozen Pop - S2-E15
Continuity mistake: When Doug goes back into the house at the start he opens the door with his right hand. Camera cuts to inside the house and now it's his left hand on the door handle. (00:01:35)
Queasy Rider - S2-E1
Revealing mistake: We see Doug crash into the fridge 3 times, thus implying that it's 3 times he's crashed. However it is the same clip used for all 3 crashes. (00:13:40)
Queasy Rider - S2-E1
Visible crew/equipment: When Doug and Carrie are arguing over the bike a white tape marker can be seen on the floor. (00:09:20)
Strike One - S3-E5
Other mistake: When Carrie yells at Doug for ruining the bathroom, she yells when she is at the top of the staircase, and we can still see her legs. There is no way she could see the problems in the bathtub from there. (00:15:20)
Visible crew/equipment: In the opening scene, when Doug almost sits on Arthur, you can see part of the blue mat that Doug rolls Arthur off the couch on to.
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.