I noticed a few times that during the first season if you look in the "hallway" of the Evans' apt. there are two very noticeable metal pipes on the walls. There is one to the left of the parents' door and the other is adjacent to the bathroom door. They appear to be those pipes that carry electric wiring from one place to another. These kind of pipes are used when walls are made of concrete and the electrician can't drill or insert wiring in the walls. But in the seasons after that, those pipes are gone.

Also, during the earlier seasons, there is a noticeable corner between Thelma's bedroom door and the parents' door. There is even a little stand there with some kind of lamp on it, i believe. However, in the later seasons, that noticeable corner is gone. Thelma's door is much closer to the other bedroom door, so much so, there is no room for a little table/stand.