My two year old has taken on the habit of writing everywhere there is a smooth surface. It doesn't matter if it is a pen, pencil, crayon, marker or chalk, that kid finds something to write with and goes to town. It takes him two seconds if he finds something to write with. When we catch hime he says, "I need paper."
So, because we kept catching him writing on the wall and taking away his marker or whatever, he stopped. YAY!!! ..... and then proceeded to write on the furniture:
He actually lifted up the sheet on the bed and wrote under it because he thought we wouldn't catch him. Are you frickin' kidding me!