Karen and Michael: No kids (spoilers)
I found it interesting how The Carr's had a big picture of the cat Tiny hanging up. I did not even realize that the room where Michael was doing his work in, the wall is decorated with children's wallpaper. I realized it when I listen to the commentary last night. I did noticed how Tiny was more of Karen's cat than Michael's. I first saw the film when I was teenager in the theaters. Until now I never realized the cat might be a substitute for a child. The movie never actually goes into details why Michael and Karen do not have kids but indirectly makes the viewer wonder.