Visible crew/equipment: When Doug and Carrie leave for their holiday, a stage light is reflected on the kitchen door. (00:09:30)
Factual error: Doug goes to the doctor for a check up after losing some weight. They live in New York, but the address on the outdoor sign is actually in California. (23101 Sherman Pl).
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.