Right before the waitress brings over the pitchers of beer and tells Doug that his wife is on the phone, Richie is holding his beer and in a blink his beer is on the table.
When Doug eats pudding on the couch, an empty cup is sitting upright, then is lying down in the next shot. Nobody touched it.
Two scenes are supposed to be occurring at the same exact time. While Doug waits in the baseball stands with Deacon and Arthur, Carrie leaves to buy ice cream at the snack shop. However, the same actor (an extra) appears in both scenes, as if he were in two different places at the same exact time. He is a heavy-set man, wearing a tan shirt, blue jeans, and a gold chain around his neck. In the baseball stands, he is sitting across from Doug, to Doug's left (on the right side of the screen). In the snack shop, that same actor is standing in the line to Carrie's right (on the left side of the screen).
In the row behind Doug at Shea Stadium, there is a man who continues to take bites and chew, however the hot dog is always full and unbitten.
When Doug is running away from the Shea stadium security team you can see the Mets lineup on the scoreboard. However, in the very next scene as Doug is jumping the wall, the Mets lineup is completely different. In one of the video clips of Mets action, you can see that Orel Hershiser is the pitcher. When Doug is jumping the wall, Orel Hershiser [#55] is the pitcher listed on the scoreboard. In the previous scene, Steve Trachsel [#29] is listed as the Mets pitcher on the scoreboard.
When Doug & Arthur are supposedly stuck in traffic, there is a car behind them, a blue Hyundai, clearly displaying a newer California white & blue vanity plate. Further back to the upper-left of the screen, in another lane, there's burgundy red car clearly displaying an older blue & yellow California plate. To the right of the screen there's a new white Acura displaying a local dealership temporary plate.