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.
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: 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: 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.
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.
Continuity mistake: While Alan's sitting on the couch, Evelyn's talking to Alan "helping...through a very difficult time," and in the shots facing Alan all of the books on the table behind him, and also the books on the couch's side table keep changing - not just their position, all the books actually become different books. Additionally, in the shots facing Charlie, the books beside the chair and the books/CDs/DVDs on the bookcase change as well.
Continuity mistake: While Evelyn is at Charlie's asking Alan if he's considered that there may be another man at Judith's "shacking up with her," Evelyn is wearing a blue 2-piece skirt suit, but in Charlie's close-up Evelyn's wearing a white suit with a red floral pattern when she's standing in front of Charlie, at the left side of the screen. (In the original pilot Evelyn is played by Blythe Danner wearing the floral suit, but she had to back out and was replaced by Holland Taylor, who's wearing the blue suit).