Continuity mistake: When talking to Doug in the back yard, Carries hands are changing position between instant cuts. In some shots they're together in her lap in others she's holding Doug. (00:04:00)
Train Wreck - S1-E20
Visible crew/equipment: When Carrie grabs the mail off the floor if you look in the window behind her you can see the pole of a boom mic moving around. (00:12:45)
Court Date - S1-E17
Continuity mistake: When Doug, Carrie and Ritchie are talking about the cop having not called her yet, Doug's hands are either on or off the bottle of beer, and the level of beer/foam changes between shots too. (00:16:30)
Court Date - S1-E17
Continuity mistake: When Arthur storms out saying that was his drug speech, Carrie has her wrists in the table in one shot and under the table in the next. (00:15:10)
Hungry Man - S1-E21
Continuity mistake: At the very end when Carrie walks out the level of foam on Doug's beer bottle changes between shots. (00:21:20)
Continuity mistake: When Arthur tells Carrie that he has jury duty, Carrie places her used coffee mug on the counter beside the mug tree, then her used mug vanishes, the mugs hanging on the tree change, and the coffeemaker moves. (00:04:30)
Visible crew/equipment: When Arthur walks into the living room humming the Happy Birthday tune, as he bends down to pick up the magazine, a camera is visible on the right side of the screen. (00:02:30)
Visible crew/equipment: After Doug gets Arthur out of the house he takes him to a restaurant, and as they both take their seats, the two sets of double tape marks are visible on the carpet under the table. Then, when Doug stands up another small tape mark is visible at his feet. (00:06:30 - 00:08:00)
Frozen Pop - S2-E15
Visible crew/equipment: While Doug is scraping the windshield in the wide shots, the end of the street backdrop and production equipment are visible at the upper left side of the screen. (00:01:15)
Visible crew/equipment: After Spence gets weird while taking pictures of Sara at the anniversary party, when it cuts to the wide shot as Arthur says, "Okay, Garver!" a camera is visible at the right side of the screen.
Visible crew/equipment: At the start, when Doug walks over to the corner armchair, the shadow of the moving boom mic is visible at the top, left side of the screen. (00:00:10)
Continuity mistake: While Doug is sitting on the corner armchair reading, Carrie's on the sofa holding her coffee mug and magazine, but when she tells Doug to join her on the sofa her coffee mug vanishes from her hand, and then it reappears. (00:01:00)
Visible crew/equipment: After Arthur tells Doug he wants to move back in, Doug loses it and starts to rail, then as he shouts, "How about my kidneys, I have two," a piece of equipment is visible at the right side of the screen, before it moves back out of shot. (00:20:30)
Revealing mistake: While Doug and Carrie are heading home after game night at the Palmers, they pass the street sign for Buena Vista St, twice, as they're driving up Magnolia Blvd in Burbank, CA.
Revealing mistake: When Carrie holds the paper towels, the kitchen's curtains over the sink are normal, the window is closed and the blinds are down. However, next shot the blinds are up, the double-hung window is oddly open outward sideways, and the curtain is pulled back with a large clamp. Then it's all back to the normal previous way.
Visible crew/equipment: Doug calls the phone number of the mystery guy, and when mystery guy answers his cell just a few feet away from Doug, two green tape marks are visible on the floor near Doug's feet. (00:16:30)
Visible crew/equipment: While Doug, Carrie, and Arthur are on the checkout line, Doug notices the mystery guy on another line, and two tape marks (an orange and a green) are visible on the floor near Doug's shopping cart. (00:20:20)
Visible crew/equipment: After Arthur coerces Carrie into inviting quite a few others to their dinner she reminds him of his inside voice, then, when Arthur walks away to get the gherkins in aisle 4, there are multiple visible T-marks taped to the floor behind Carrie. (00:07:05)
Continuity mistake: In the first shot inside Arthur's house, Carrie and Doug are standing together when Carrie mentions how tough it must be for Arthur. It then cuts to Arthur sitting at the table, with Doug right there sitting beside Arthur. Next shot Doug is still standing with Carrie as she urges Doug to spend some time with Arthur, so this is when Doug walks over to his father-in-law. (00:07:00)
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.