Jon is still acting "normal" because he made the wish so he is aware of everything that's changing with him. With other people they are aware but not as much as Jon (if that makes sense). As for the changes, I wanted it so that it would be different with each person so as not to become repetitive.
So for example while it might start with underwear with one person. It might start with something else with another. Also I think it might make sense that if Sharon is swapping with her daughter then her emotions would be more affected than other swaps.
