After installing a new toilet in a bathroom remodel project I looked at the box and said that looks like Thomas the Train. A grandpa of seven knows what Thomas looks like. (If you have trouble throwing away a cardboard box you may have some hoarding tendencies)
For every 2-3 real projects you should do one just for the heck of it funproject.

Step 1: Wheels

If you are a grandpa of seven you may have a collection of power wheels spare parts laying around. Since this is a quick fun project I decided I had to use whatever I had in the workshop.

Step 2: Frame

I used some spare 2x6 and plywood to form a frame to attach the rear axle and the front suspension section.

Step 3: Wheels to Frame

Drill holes in the 2x6s to slide the rear axle through. I drilled holes and used the original PowerWheels front suspension section mounting holes and screws.

Step 4: Steering Wheel

I used the original power wheels steering shaft and steering wheel by drilling a hole at a 45degree angle in the plywood frame floor.
I also built a support bracket for the steering shaft that would mount inside the box with drywall screws. This bracket doubles as a way to mount the cardboard box to the wood frame by sandwiching the cardboard between the frame and the wooden bracket. I also used a piece of plywood to similarly fasten the back of the box to the frame.

Step 5: The Body

I used glue and packing tape to put the box back together. Then cut out openings for the windows and door.

Step 6: Paint

Search google images for Thomas the Train so you have an idea of the paint scheme. I mixed some dark blue and white paint to get close to a Thomas color blue. Then I painted the outside blue.

Step 7: Face

Thomas has a smiling face on the front. I cut circles out of cardboard and glued them together to get the extended tank look. I glued and used drywall screws (from the inside of the box) to attach the tank/ face.
Ok this step is out of sequence but you get the idea

Step 8: Trim Paint

Thomas has red, black and yellow accent paint and a yellow number 1 on the side.
I added a smoke stack by wrapping a cardboard paper towel roll in black electrical tape, cutting a circular hole in the top and inserting the smoke stack.
This does now use a battery or motors rather this is designed to be powered by dad or big brother or sister.
Ok so it's not perfect but I think the grandkids will recognize Thomas.