Continuity mistake: When Bree is about to leave the hospital she picks her bag up with her left hand to put it on her right shoulder but when the camera angle changes she's put the bag on her left shoulder with her right arm.
Continuity mistake: When Bree is talking to Mike in hospital, the position of her roll neck jumper on her right shoulder changes constantly throughout the scene. In some shots it's rolled down, in some it is rolled up.
Chosen answer: Poker. They have been playing that this whole time, once a week with everyone who was invited that lived on the Lane.