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)
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.