Step 1: Pepakura Viewer
I have made Thomas' helmet, but if you are looking for a challenge, use some of the tips from this instructable to make Thomas' helmet.
First, you will want to download Pepakura Viewer, which is a program that lets you view paper craft items that other users have made.
Once you have downloaded Pepakura Viewer, download Thomas' helmet, here. I didn't build the full helmet, as I knew ahead of time that my head was too big for the paper version. So I improvised, and used a hard-hat as my base, and attached the front of the paper helmet to it with masking tape. I'm sorry that I don't have any build pictures of the paper helmet face part. When cutting out the shapes, each edge has a number, which you tape/glue/attach to the corresponding number.