Continuity mistake: In the scene where Joe Nast goes to the post office to get back the wedding invitations, Bertie invites him to come through the little window into the back to help her find them. As he crawls through he accidentally kicks the bell off the counter. However when the shot changes to the interior of the mail room, the bell is still on the counter. The DVD commentary states that this shot was done on a stage in a studio, and the former shot was an actual store. Jake Gyllenhaal admits to having purposefully tried to knock the bell off, so it seems that when the studio shot was being made this detail was forgotten, or it was shot beforehand.
Other mistake: When Joe was dropping off Ellen Pompeo after she delivered the last wedding invitation, it was raining and the windsheild wipers were very loud but as soon as they started talking they stopped being so loud.
