See what a difference the paint makes? Pick a lighter colored blue for your Thomas though. This cadmium blue is darker than Thomas should be. The whistle, buffers, and numbers are cut out of craft foam ("Foamies"), and they add some nice dimension, I think.
The next step is to add straps so your train engineer can wear Thomas. I used peel and stick velcro. I cut four small strips (the prickly side of the velcro) and put them inside the train.
Then I used the soft side of the velcro for the straps. This way, your straps are completely adjustable. They can be worn straight across the should or crossed in the back. I left the peel away paper intact on the straps.
When I did a test run on the costume I found it was back heavy. To add ballast (?), I taped a 16oz can onto the inside of Thomas' head. This worked very well, but it did make the costume pretty heavy for my little guy. If I were making it all again, I'd make the back of the train much thinner and forgo the extra piece to cover the seams. Try to make it as light as possible. You might also cut the engineer opening further towards the rear of the first box, rather than in the middle.
The only remaining step is Thomas' face! You can print out a face from
this website. I believe this is actually James' or Percy's face. If your little one is old enough to tell the difference, you can change it to look more like Thomas by drawing more of a triangular eyebrow with a black marker. My guy didn't care. To fit my "head" I printed out the face at 80%. You may have to fiddle with this a bit to get the right size.
As you can tell the costume turned out to be too large for my 2 year old. These instructions make a train that would better fit a 3-5 year old. If your person is smaller, be sure to start with smaller boxes! Comment with any questions you have about the process, and I'll try to clarify!