I just finished watching the episode in syndication and I think it's one of my least favorites of the series. On one hand, it's really cute with Cliff planning to build Clair an extra room, a much deserved and needed room. Every kid is selfishly demanding their attention, and I like the way Cliff immediately lays down the law of the new house extension is solely "Your Mother's room!!" No kids allowed. But all of this is overshadowed by what Sondra and Elvin pull, bullying Cliff and Clair into letting them and their children stay in the already overcrowded Huxtable house. It only strengthened my view of especially Elvin being one of the most annoying characters ever on tv.
This shows how cowardly Elvin is for when there's trouble with getting the new house, he can't buck up and be the head of his family, nope, he has to impose on his inlaws for support. What about his own parents? Both he and Sondra stoop to using their own kids to get their way to stay with Cliff and Clair. Then they even come up with an arrangement where they can get a bedroom to themselves. Family can be family, I know, but they shouldn't take advantage and be bullies with other members, especially the parents.