OK so I know preschoolers are a bit OCD but my son seems to have taken this to a whole new level recently.
He is obsessed with toys being placed in the "correct" way - particularly his little sisters toys - which means they can't be played with. He gets really quite upset when, for example, a spinning toy spins and ends up facing a different way.
He's also started to get very upset when my DD kisses me, or him, saying that he doesn't want us to get wet. Again this seems to lead to real upset rather than just plain naughtiness.
There have also been a few problems like this at preschool and he sometimes seems to genuinely antagonise other children 
So is this normal? Do I wait it out or try and encourage less rigidity in this thinking, and how?