A change that has occurred in a very natural way, which has been almost imperceptible, is how the boots or shoes of some characters are drawn. While nowadays animators are going for a more curved or softer style in their forms, previously we all remember the peak-shaped tips that characters used to have.
It's not a relevant change at all, but it's a sign that the series evolves, that the series changes, for better or for worse, it's not static.