Character mistake: Carol says that Michael proposed to her on their fourth date. The proposal happened in Season 3, Episode 6, Diwali, and in that episode, Carol mentioned that it was their ninth date.
Character mistake: In the scene where Ryan and Andy are taking a tour of Gabe's bedroom, Ryan says "Hey, Marantz tube stereo from the 1970s" It is in fact a Marantz SR 1000 stereo receiver. This model uses solid state electronics, not vacuum tubes. (00:13:30)
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.