Character mistake: Meredith admits during the ethics seminar that she has been sleeping with Bruce, the HammerMill rep, for discounts on paper/paper supplies for the company, as well as Outback steak coupons, for 6 years. But, Dunder Mifflin did not begin selling Hammer Mill products until 3-2 "The Convention" when Michael got the contract.
Continuity mistake: In 2-13 "The Secret" Pam and Jim are talking about how Jim used to have a crush on Pam when she first started here. This implies that Jim was working here when Pam was hired. However, in this episode Pam says that when Jim first started working there she said, "Enjoy this moment, because you're never going to go back to this time before you met your desk-mate, Dwight." These two scenes contradict each other.
Continuity mistake: In one episode Angela says she hasn't talked to her sister in years over an argument that she doesn't remember. When she's engaged to Andy and they're touring Dwight's farm he mentions she has multiple sisters. In the finale she only has one sister and apparently they are incredibly close.
Continuity mistake: In "The Alliance" (1-4), Pam says that the next office birthday is Meredith's, but it isn't until the next month. Later, in "Survivor Man", it is said that Meredith's birthday is at the end of 'Birthday Month', when many employees have birthdays close together. It wouldn't be possible for Meredith's birthday to both be the next office birthday but also at the end of the following month, which is stated to have many other birthdays in it.
Continuity mistake: In 4-14 "Goodbye, Toby", Andy Bernard invites his parents to the going-away party for Toby Flenderson and introduces them as "Andrew and Ellen Bernard." But in 6-16 Andy tells Jim that he was originally named "Walter Jr." after his father and that it was changed when his little brother was born and the name Andrew was one that they got out of a baby-naming book. Additionally, in 8-4 "Garden Party", Dwight is introducing the entering guests. When Andy's parents arrive, Dwight says, "Mr. And Mrs. Walter and Ellen Bernard." (00:36:20)
Continuity mistake: When Jan, Michael and Pam are having a meeting in Michael's office they're sitting against the front window, but during that scene when it shows Jim and Dwight talking at their desks, if you look over Jim's shoulder you'll see that the office behind them is empty. (00:06:30)
Continuity mistake: When Michael enters the room he messes with Jim's hair and Jim's hair is noticeably different, however a few different camera angles later Jim's hair is back to normal even though he couldn't have possibly had time to touch it. (00:09:10 - 00:09:50)
Continuity mistake: When Michael takes Katy (the purse lady) around the office, she worries about leaving her purses unguarded so while walking by Phyllis and Stanley's desk clump he asks Ryan to look after the purses, but Ryan says he can't because he's "installing File-Share on all the computers." Phyllis is noticeably absent from the shot. Ryan is sitting at Phyllis' desk. Michael and Katy take a few steps and walk into the kitchen area. In the background we can now see that Phyllis is now sitting at her desks and Ryan is nowhere in sight. There wasn't enough time for both to switch locations like that as only a moment had passed between the shots. (00:06:10)
Revealing mistake: When Toby announces that he's moving to Costa Rica, he gets up and goes to hop the fence. He moves out of frame and when the camera goes back to him, he's been replaced by a stunt double, which can be seen as the double's face is visible after he's scaled the fence. (00:17:15)
Continuity mistake: When the Dunder Mifflin lawyer says "she thought it had to do with her recent breast enhancement surgery," the woman on the right side of the screen has her hand on her forehead. Then the shot changes angles and the woman's hand is now resting on her chin. (00:08:45)