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."
Continuity mistake: At the end of the episode, we are shown a video of Dwight getting splashed with the milkshake from the point of view of the guys in the car. But it splashes differently the two times we see it. The first time it hits his lower body, and on the video, it hits him in his upper body.
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 Season 3 Episode 2 The Convention when Michael got the contract.
Continuity mistake: After the banker asks Toby if there is any inappropriate behavior, a few seconds later there is a flash back of Season 3 Ep. 22 when it is the beach games and Michael is hosting a hot-dog eating contest. Michael says to Phyllis to "Dip it in the water so it'll slide down - your gullet more easily." In the flashback version, everyone says "That's what she said." In the real version, no one says anything. Not to mention Toby wasn't actually at the beach day, Michael told Toby to stay because "Someone needs to stay at the office."
Continuity mistake: Nellie and Pam are driving along, discussing what to make up about people's ancestry. Here, we see the same background go past Pam, a driveway with a black SUV on the right, and a white SUV on the left. This shot is only repeated in the angle where we can only see Pam, and the view out of the passenger side window. The car is driving along as normal, we see the two cars on the driveway, and then the car turns a corner, and we see the same shot all over again.
Character mistake: As Michael is getting ready to propose to Holly, he stops in the foyer and says, "This is where Toby announced that he was going to Costa Rica. Happiest day of my life." This is a discrepancy, as Michael was in New York partying with Ryan and Dwight when Toby made this announcement.
Continuity mistake: After everyone but Dwight and Kelly exit the building (because of the fire), Dwight picks up the water jug and accidentally knocks over the blue cups next to it. A few cups fall to the floor but one remains still on the printer (next to where the jug was). After Dwight gets Kelly out of the kitchen, the blue cup has disappeared from the printer.
Continuity mistake: When the office is hyped up on espresso, they try to move the copier to the annex, consequently ripping up the carpet. Oscar says that he always knew there was hardwood underneath but never thought he'd live to see it. This contradicts Season 7 Episode 23 when Dwight shoots a gun into the floor, and Oscar is offended that they would have covered the beautiful hardwood he noticed under the carpet when inspecting the bullet hole.
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." Both Stanley and Phyllis are noticeably absent from the shot. Stanley's desk is empty and 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 both Stanley and Phyllis are now sitting at their desks and Ryan is nowhere in sight. There wasn't enough time for everyone to switch locations like that as only a moment had passed between the shots.
Continuity mistake: During the basketball game just before Pam throws the jump ball, Stanley is seen standing over Pam's left shoulder. After she tosses the ball up Michael hits the ball mid-air over to Stanley who is now about 10-15 feet in front of Pam, with no time to logically get there between shots.