Continuity mistake: When Gabrielle and Carlos go out of the house to investigate what is happening when the Chinese maid starts shouting, they close the door behind them. In the following shots the door is open again.
Continuity mistake: While Betty Applewhite is talking to Bree about her son Caleb, the amount of wine in Bree's glass changes constantly throughout the scene without her ever touching the glass.
Chosen answer: Poker. They have been playing that this whole time, once a week with everyone who was invited that lived on the Lane.