My daughter's preschool had a transportation parade this year where each child had to wear some form of transportation and the parents got to help them build it.
My daughter and I searched the web and she decided on her own that she wanted a pink and purple train and that's exactly what she got.
We started by collecting some good size boxes and created the frame
She helped me paint the entire thing in pink paint that we picked up at the local hardware store. I bought purple tape from the craft store which made the striping part way easier than painting them. It was essentially blue painters tape but in purple.
I used a toilet paper roll and paper bowl for the smoke stack
The wheels are just cardboard cut out to circles and painted
I added some cotton balls the day of the parade for the smoke