Continuity mistake: This is a very tricky one to spot as it happens as the shot is fading into black to a scene change but it is noticeable without the use of pause and/or slow motion. When Doug and Deacon are outside talking, Carrie comes out and then proceeds to walk back in and and audibly shut the back door. However as Doug and Deacon walk back in as the shot is fading away, the door is wide open. (00:09:30)
Continuity mistake: When Carrie is reading from the leaflet, the way she holds it changes depending on the shot. (00:17:35)
Inner Tube - S3-E17
Continuity mistake: At the start at IPS, Doug's tie is looped over itself twice. Camera cuts and now it's not looped at all. (00:02:30)
Inner Tube - S3-E17
Continuity mistake: When Arthur brings the tray to Doug in bed, the position of the duvet/sheet is constantly changing. (00:06:20)
Continuity mistake: When Carrie turns round and tells Doug that she's telling Kelly about the card, the bottle top on the table is constantly changing position without being touched. (00:11:40)
Continuity mistake: When Carrie is unpacking the shopping at the start she holds up an empty bag that magically folds itself flat between camera cuts. (00:01:50)
Continuity mistake: When Doug is writing on a board, he holds the board at the end or the top depending on the shot. (00:03:30)
Continuity mistake: When Stephanie arrives and Doug says about killing his parents, Stephanie has her hands apart, but when the camera angle changes to a different view, her hands are clasped together. (00:14:40)
Continuity mistake: The Saskeys are Doug's neighbors in this episode despite them having moved away back in the season 2 episode "Soft Touch" (00:02:30)
Continuity mistake: When Tim and Doug are talking about the pool overlooking the property, the way Tim holds the ball changes between camera cuts. (00:15:00)
Continuity mistake: When Carrie realises Doug has been in the pool, the magazine in Doug's hand vanishes instantly. (00:18:20)
Continuity mistake: When the beach ball sails over the fence, Doug picks it up and holds it to his face, making his right side of his shirt wet. Throughout that scene, his shirt is dry, and then wet again.
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.