Weight Loss - S5-E1
Character mistake: Pam attends her first class and notices she is in the wrong class. Written on the whiteboard is the title of the course and the name of the teacher. While obscured, you can see it is supposed to say "Professor Monaghan." Written on the whiteboard is: "Proffe [obscured] ghan." Professor is spelled with one F. (00:09:05)
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.
Baby Shower - S5-E3
Continuity mistake: When Jan lets Michael finally hold Astrid, she has a pacifier. When Michael gives her to Phyllis, Astrid's pacifier is gone.
Continuity mistake: When Meredith's hair catches fire, we never see her face (as it's a stunt double). After Dwight uses The Fire extinguisher on her, the shot cuts (although she is still in the frame) and her hair is different, as it is now the original actor that plays Meredith. (00:05:50)
Continuity mistake: Michael's scarf is above his collar in the first shot, but moments later, seemingly without moving, his scarf is tucked below his collar. (00:06:40)
Plot hole: When Andy duels Dwight, it doesn't make much sense for the office employees to not be outside watching The Duel. On other occasions, like Pam hitting Michael, they did watch outside. To not have any one of the office workers watch or even supervise the situation, including Jim, who acts concerned throughout the unfolding ordeal, is unlikely. The reason everyone stays in is so Andy's plan of blindsiding Dwight with his car can work out.
Lecture Circuit: Part 2 - S5-E15
Continuity mistake: When Jim and Dwight are talking about the activities for Kelly's party, Dwight is attempting (horribly) to blow up a silver balloon. Just after Jim finishes reading The List of proposed activities, Dwight says, "You're right, forget horse hunting, it's stupid." Immediately after he says this, the shot changes and he is now holding a brown balloon. (00:16:30)
Suggested correction: Michael didn't establish the contract with Hammer-mill. Rather, he locked them up as an exclusive supplier. It's unknown if they were already selling the products to Dunder Mifflin alongside Staples and Office Max.
Wrong, Josh says they cannot sell Hammer-mill products as they are exclusive to Staples so therefore they wouldn't have been able to sell there products alongside as mentioned before until Michael made them an exclusive to them solely, Dunder Mifflin. Therefore the original mistake stands true.