Visible crew/equipment: Near the beginning when Doug comes into the kitchen and smashes the cake with the watermelon, you can see a stage light reflecting in the door window 3 times as it swings open. (00:00:10)
Revealing mistake: During both opening and closing driving scenes, a light on the back and top of Doug and Carrie's heads slowly flickers on and off but never moves - revealing a stage light simulating driving past street lights. (00:00:20)
Revealing mistake: When Doug and Carrie are waiting in line at the DMV, a man (casting extra) can be seen just outside the doorway waiting to enter the scene. When the shot changes and Doug and Carrie approach the counter, the man casually enters the set. (00:03:30 - 00:04:00)
Continuity mistake: When Doug is putting lipstick on Carrie, the way she is holding her arms changes between shots (crossed then uncrossed). (00:14:50 - 00:15:40)
Visible crew/equipment: Throughout this episode you can see stage lights reflecting off Carrie's glasses - most notably in the bedroom when Doug finally convinces her to join the party. She looks toward the camera and a series of stage lights are reflected very evidently. (00:16:25)
Continuity mistake: When Carrie takes Doug into the back yard to yell at him, after she is done swinging at him, she puts her hand up to her chin. First it's her left, then right. It changes between shots. Each time the camera goes back to her it happens.
Other mistake: At the end when Doug takes the bandages off Carrie's face, the bandages come off far too easily as if they weren't really attached in the first place.
Mean Streak - S4-E3
Continuity mistake: When sat at the table at the start, the bottle top keeps changing position in relation to the edge of the table. (00:03:00)
Mean Streak - S4-E3
Visible crew/equipment: After giving an interview Doug walks over to Deacon and a tape marker from earlier in the scene is visible on the floor. (00:05:20)
Mean Streak - S4-E3
Continuity mistake: When Doug is talking O'Boyle about the old guys, the time on the clock goes back. (00:05:30)
Mean Streak - S4-E3
Visible crew/equipment: Doug is debating smashing the woman's parcel. As she opens her door a black tape marker is visible on the floor. (00:15:50)
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.