Time Share - S1-E22
Continuity mistake: When Doug Carrie and Ritchie are in the kitchen discussing how long Ritchie has to keep seeing Dorothy, Doug is making a snack involving some lettuce. The size, shape and position of this lettuce is constantly changing between subsequent shots. (00:15:20)
Continuity mistake: At the start when Arthur is ranting to Doug, the way Doug holds his coffee flask differs ever so slightly between shots. (00:07:00)
Frozen Pop - S2-E15
Other mistake: When Arthur decides to sleep upstairs instead of downstairs, he brings along a can of beans for a snack. It then cuts to an exterior street shot, which should be somewhere in Queens where the Heffernans live, but instead it's a shot of the corner at 14 Ave and 73 St in Brooklyn (some areas of Brooklyn and Queens may appear similar). Next shot is inside the Heffernan house in Queens. (00:11:45)
Continuity mistake: Doug comes out from the payphone and asks Carrie where did everyone go. When Carrie replies, the way she holds her glass changes between shots. (00:17:50)
Fixer Upper - S1-E12
Continuity mistake: When Doug is talking to Spencer in the subway, the people in the line behind him change instantly from 2 men to 1 man and 1 woman. (00:19:30)
Head First - S1-E6
Continuity mistake: When the gang walk into Coopers, a woman and man are talking outside on the street. When the camera changes to focus on Arthur a second man has appeared next to the other two and should have been visible in the first shot. (00:03:40)
Continuity mistake: When making a PB&J sandwich, the jar of peanut butter rotates by itself. Note the label. (00:09:30)
Continuity mistake: When Doug falls off his chair his right arm is on the floor in one shot and on the desk part of the chair in the next. (00:09:10)
Continuity mistake: When Doug puts down the remote to grab Carrie's Walkman, the position of the remote changes between shots. (00:00:45)
Food Fight - S4-E13
Continuity mistake: When Arthur tells Doug to eat some salad he is either holding the bowl or not depending on the shot. (00:18:40)
Continuity mistake: When looking at the quote for the repair bill, its position on the table in relation to Kelly's menu is constantly changing. (00:08:40)
Continuity mistake: When Doug says he was reaching for a fig newton, the way Carrie is stood changes between shots. Note her right arm. (00:04:50)
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.