When Helen and Jessica are arguing outside the shop, you can see people in the background looking at them. Obviously these weren't extras, but bystanders who stopped on the street to watch the movie being shot.
When Jessica and her mother are getting their bridesmaids dresses fitted, Helen is upset to learn that Jessica never mentioned her brother's upcoming wedding. But the wedding would surely have been discussed at the Shabbat dinner at the Steins' that Helen attended three months prior.
During the opening credits, when Jessica is pouring sugar into her coffee from a yellow box, the Domino brand name on the front of the box is covered with white paper, but you can still clearly see the Domino brand on both the bottom and the side of the box.