Definitely A Milhouse Divided is really one of those very special episodes that is the hallmark of many series like Diff'rent Strokes an The Facts of Life, and I think the separation of the Van Houtens really hits hard on fans who went through the divorce of their parents init. Anyway, if you were to introduce The Simpsons to someone who hasn't watched it before, I wouldn't recommend they start with A Milhouse Divided, as it's a bit too depressing and it could trigger init. Anyway, I guess The Simpsons wanted to focus on reality and they did so very much with A Milhouse Divided and the social impact.
Review of A Milhouse Divided
