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: 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.