Continuity mistake: Alan is sitting at the kitchen table talking to his son Jake about a math test on which Jake got a bad grade. At the beginning of the scene Alan holds the open test in his left hand. When the camera switches back to him a second later the test is now in his right hand. Finally at the end of the scene the test is back in his left hand but is now folded. (00:04:50)
Continuity mistake: When Alan and Charlie are watching Judith take off her clothes on the monitor screen, Alan takes the newspaper he has in his right hand and puts it in his left hand to turn the monitor off. The next shot shows Charlie walking into the kitchen and Alan looks at him but now the paper is back in his right hand.
Continuity mistake: When Charlie and Berta are in the kitchen talking, Charlie sits down and places his coffee mug on the left side of his plate. A few shots later he is seen placing it again except this time on the right side of the plate. Then just as Berta exits the kitchen, Charlie's mug has now switched sides again, being on the left side of the plate. (00:04:10)
Continuity mistake: During this whole episode, Jake calls his mother's boyfriend Greg. But in the 4th season when Judith is marrying the guy, he is called Herb. We know that it is not two different people because they both have the last name Melneck, and they are both Jake's pediatrician.
Continuity mistake: Alan throws a bra onto the floor after Charlie tells him whose bra it is, which lands touching a rug. Alan goes to pick it up and the bra has not only moved away from the rug but it is also lying in a different position. (00:12:00 - 00:12:40)
Continuity mistake: Right on 21 minutes into the episode, when Charlie and Jake are in the car, Alan comes in with food and coffee, but doesn't close the car door. After he's handed Charlie the food and coffee, they change camera angle and you can see the door is closed. (00:19:55)
Continuity mistake: When Alan comes into the kitchen singing his song, he reaches into the fridge and grabs a jug of orange juice. He then looks around the kitchen and sees that everybody seems to be in a bad mood. The jug of orange juice is gone and he is holding what looks like a jug of juice, but it had a screw lid on it and is full as if it has never been open. After talking for a few seconds the camera goes back to Alan and he is holding the jug of half empty orange juice again.
Continuity mistake: When Jake and Alan are in the car, They are talking about having Chinese food for Christmas dinner. When doing so, the car behind them changes from a black 4x4 to a red sports car. Then back. There is not enough time between shots for the cars to maneuver.