Continuity mistake: Emily has a bad cold/flu the day of the benefit Miranda hosts - her nose is extremely red and she's congested. Miranda tells her Andy will have to go too, so Emily shows Andy photos of clients to memorize; suddenly she has no sign of a cold at all - the redness just disappears, which wouldn't happen that quickly. That night it's back in full force, just as it was earlier in the day.
Continuity mistake: Not only does Andy not have the bagel when she enters the subway stairs, but she is wearing her gloves/mittens when she does - when the bagel reappears, they are gone.
Continuity mistake: In the restaurant where Andy is giving her friends presents, she hands her friend a little clear case of Clinique products, but when she's putting them in her friend's hand, she is also holding a blue box when she wasn't before.
Continuity mistake: At her first day of work, Andy is telling Emily about Miranda's demands, and as Emily asks "Did she say which skirts?", her arms are on her hips, but as the shot changes, her arms are folded in front of her, with no time for the shift.
Continuity mistake: When Andy answers the office phone for the first time, the blue post-it notes that had been right next to the monitor's base, have moved a couple of inches, even though no one touched them.
Continuity mistake: When Emily is saying "This is what you are doing" and closes her hand, her pinky and her ring finger are up. But in the next shot, shot from the back of her, her pinky and ring finger are closed. In the next shot, in front of her, her whole arm is down. There is no way she could have put down her hand that fast.
Continuity mistake: When Andy goes to the fashion party on Nate's Birthday, her hair ornament is a white butterfly, but when she gets home it has changed to a white flower.