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
Continuity mistake: When in the garage, the way Carrie's arms are crossed changes instantly. (00:09:50)
Continuity mistake: At the start of the episode when Arthur is on about kissing ass, the way his napkin is positioned constantly changes. (00:03:45)
Continuity mistake: At the beginning Carrie is dishing out potatoes from a bowl with a large black spoon, and as the camera changes angles her arm has not moved and she is now holding a small fork getting chicken from a different bowl. (00:01:40)
Queasy Rider - S2-E1
Continuity mistake: When Doug is checking Arthur's CV at the start, the items on the counter keep moving - noticeably the mayo and lid. (00:00:25)
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.