Continuity mistake: In the opening scenes, Grace has red nail polish on. Later in the same scene, it has vanished as she shakes Mrs. McFarland's hand. (01:03:20 - 01:06:15)
Continuity mistake: When Grace is preparing the food for the thanksgiving dinner, she unwraps the plastic wrapping from the bowl of cranberries, and scrunches it into a ball. In the next shot she holds it and it is unwrapped and not a ball anymore. (01:10:25)
Continuity mistake: When Jack is lying on the table, with the huge bowl on his face, the position of the boxes behind him on the table changes a few times. In one shot they're half hanging off of the table, in the next shot they're fully on the table etc. (01:08:15)
Continuity mistake: After Will tells Jack that he knows that he hasn't told his mum he's gay, Jack backs into the patio doors, and the blind unrolls itself. In following shots it alternates from rolled up / down. (01:07:30)
Continuity mistake: During the thanksgiving dinner, Will is mixing salad. He then leaves the mixing spoons in the bowl. In the next shot they've vanished, and then reappear later on in the scene, back in the bowl. (01:14:00 - 01:15:35)