At Luann's pool party, Peggy comments there are no more hamburgers, when there is clearly a plate of them behind her on the table.
The events depicted here begin with the guys going to Dallas for Bill's birthday, making it clear that this is meant to be a celebration for his birthday. Things then take place over the course of what is most likely a few weeks, with Bill dating Ann Richards, and eventually beginning to date Lenore again. Yet the BBQ at the end is supposed to be for Bill's birthday. Why would they celebrate Bill's birthday SEVERAL WEEKS after it happened?