Revealing mistake: After the opening credits there is a shot showing the house on the island where Karen and Stan live. If you look at the hanging chair, you can see that Karen is sitting in it. But in the very next shot she is in a meeting with Will, in a different outfit. This is a re-used shot from the previous season, which shouldn't be there.
Revealing mistake: In reality Deborah Messing is pregnant but her character is definitely not, so Grace has been filmed lately hiding behind big purses, pillows, counter tops, coats, etc. For some reason in this episode there was some rather sloppy shooting where Grace's waistline is concerned: When she and Karen are first entering the cabin, right after Grace says the line '...driving past 20 churches...' she turns sideways and for a few seconds there is a clear shot of her advanced pregnancy. Additionally, when Grace and Karen go to bed (also in the cabin) they have Grace lying on her back so the pregnancy is quite obvious in that scene, too.
Revealing mistake: At the very start when Will enters the coffee shop, he walks over and asks the server for a coffee. The server picks up a mug, pretends to push the coffee machine button, holds the mug under the machine for about two seconds and hands it to Will. To top it off you clearly see nothing go into the mug.