Queasy Rider - S2-E1
Revealing mistake: When Doug comes in at the start and says he has been riding Ritchie's hog, all the stage lights can be seen in Carrie's wine glass. (00:02:20)
Queasy Rider - S2-E1
Revealing mistake: When Doug comes into the garage the first time, if you look through the garage door, at the end of the fence is a very noticeable crease running vertically. This shows the outside is a fake. (00:06:55)
Queasy Rider - S2-E1
Revealing mistake: When Carrie and Doug are in the garage arguing about the bike, there is a shot of the fridge where tyre marks and a dent are visible. However we later see Doug make these marks. (00:09:00)
Queasy Rider - S2-E1
Revealing mistake: When Doug is seen giving a lift to Arthur, and Arthur is holding on very tight, the background is so very projected. (00:13:05)
Queasy Rider - S2-E1
Revealing mistake: We see Doug crash into the fridge 3 times, thus implying that it's 3 times he's crashed. However it is the same clip used for all 3 crashes. (00:13:40)
Queasy Rider - S2-E1
Revealing mistake: Doug falls off the bike at one point and shouts that he has had enough. He opens the door and if you look carefully a stage light and boom mic are reflected in the glass. Slo-mo may help but is not essential for spotting the mistake. (00:15:25)
Revealing mistake: During the scene when Doug is "out with the boys" driving in Spence's car, you can tell they are actually in a studio using a green-screen because the stage lights reflecting off the car don't move. (00:36:00 - 00:36:35)
Revealing mistake: When Doug tells Arthur his toast is done, there is no smoke, but as soon as he is finished speaking there is smoke coming from the toaster. (00:04:05)
Revealing mistake: When Carrie phones Doug at IPS, Doug goes to press the button on the phone for the correct line, but doesn't press any and continues to talk to Carrie. (00:07:40)
Revealing mistake: Just as Arthur goes to look in Carrie bag, there is a wide shot and a cabinet can be seen by the door. In the glass of this cabinet's door, you can see a stage light reflected. (00:11:45)
Revealing mistake: When Arthur is looking in Carrie's bag, there is one shot with a blue kettle next to the bag. 10 stage lights can be seen reflected in the kettle. (00:11:50)
Revealing mistake: When Doug and the rest are at a ballgame, the man sitting behind them is eating a hot dog. Actually he's pretending to eat, it never shows any bite marks and the guy is pretending to chew it.
Frozen Pop - S2-E15
Revealing mistake: When Doug goes out to scrape frost off the car, we can see he casts 2 shadows from different stage lights as he comes down the steps as well as on the hood of the car. (00:01:00)
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 driving to find the dog, neither Doug nor Carrie's hair is blowing in the wind - even when they're on the back of the convertible. (00:18:00)
Revealing mistake: When the lights go out at the end of the episode, there is a reflection from a stage light very visible. (00:20:30)
Big Dougie - S2-E21
Revealing mistake: When Doug is jogging in the marathon he is casting three shadows in different directions. Also, the female jogger behind him appears to be in good shape but is still jogging as dramatically slow as Doug. (00:19:20)
Revealing mistake: After Doug successfully trades vacation days with Roger, it cuts to Doug's IPS truck stopping in traffic. The next few shots were filmed on the streets at Sony Pictures Studios lot. In the shot of the IPS truck's side-view mirror (as the RV approaches), note the signs on the building read "Keaton Building" and "Sound Department Courtyard." After the flashback, another building sign reads "Durante Building." These buildings are located at the north side of the studio in Culver City, CA. (00:03:20)
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.