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.
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)
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.