There was a period of 6-9 months when Nate would line everything up. Books, toys, whatever. He'd systematically put multiples of things in a row, horizontally or vertically. I started taking pictures of them. I was a little worried about OCD but now he doesn't seem as interested and, in typical boy fashion, prefers to mess stuff up instead of tidy up. Here's what I'm talking about:
Crayons. He wouldn't use them, just put them in a line.
Spools of thread.
Even poor baby Jesus has to stand in a line.
My pots and pans. Personally, I think he's trying to cover up the hideousness that is our kitchen floor.
This one is my favorite. Nate was eating lunch and I went to my bedroom to get something and discovered this line of film rolls (remember film??) on the floor. It surprised me and I almost stepped on it. I kinda felt like a farmer discovering a crop circle....