Tranformers's Bumblebee was a challenge he gave me. We wanted him to tranform too - from car from crouching, to standing robot. I looked online and parents have out done themselves with really amazing transforming costumes, but as usual, I like to look around the house and see how close I could come with boxes, yellow duct tape, poster board, and craft foam.
I punched a hole and used nut & bolt to create a hinge for the hood of the car to flip up so his head to poke through. We had these disks that were supposed to teach him how to catch which were black that he wore on his hands for the front wheels.
Bike reflectors doubled as head and tail lights, and made it safe for trick or treating in the dark as well.