This is a walking toy with 6 legs which uses a simple linkage found elsewhere. You only need 2 screws (M3), one with length 15 mm and the other 30 mm, for the gears' axles. For the motion source, a DVD or CD motor can be used. Place for batteries not included, anyway... I have to think where to put them. Single lithium ion cell at 3.7V is enough to propel the thing. Maybe a 9V battery will do too.
For a complete set, print 2x frontaxle (which is identical to back axle), 4x frontleg, 2x midleg, 6x connector and 1x all others.