OBSESSION!!

Okay...is it normal for toddlers to have obsessions? Not interests, but full on, talk about it all the time, obsessions.
We currently have two.
#1 TRAINSJack LOVES trains. After school each day we drive over train tracks. From the time he gets in the car until our tires hit the tracks its: "choo, choo?? choo, choo??"
Then, as soon as we get home, he's running to his trains and wanting to watch Thomas.
We love that he loves trains so much, but we're hoping Thomas phases out soon. That tune sticks on your head like CRAZY!!
Needless to say, there is a birthday party coming up that's being held at the train depot!

#2 "Writing" with pen and paper
We were at the grocery store one day and Jack was NOT wanting to stay in the cart, so I gave him a pen and a post-it pad that I had in my purse.
BIG MISTAKE! We now have some ruined clothes due to ink stains.
He loves to have pen and paper at all times! Not crayons, markers, coloring books, no thank you.
Tonight he cleaned out mom's purse. He got all the old receipts and an old grocery list out, laid them out and sat there for almost 30 minutes talking to Pooh about whatever he was writing.

God, I love him to bits!