This train (runs on track or carpet) has a different face when you turn it around.

More information is available at:
http://www.instructables.com/id/Two-Face-Train/

Print the body, then print 4 wheels and 4 hubs.

Place the wheels on the axle, then superglue the hub to the end of the axle to hold the wheel on.

Paint the faces and hubs as shown--or to your liking.