Visible crew/equipment: When Doug and Carrie are talking about the sketch of Carrie on the fridge and Doug says, "Man, he's got some skills" (talking about Major), a boom mic is visible at the top of the screen.
Continuity mistake: When Danny interrupts Deacon and Kelly's dinner the couple retreat to their bedroom, and while Spence mumbles to himself as he clears the plates, in the closeup he places some plates on the pass-through shelf, but those plates have vanished in the next wide shot.
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.