Here I recommend one interesting kit: "DIY Walking Robot"

Product Size:8cm*7cm*7cm(Length*Width*Height)
Material:Environment-friendly plastic,metal
Packaging:Bag(with a Chinese instruction)
Battery:The kit does not include a battery, you need to prepare 1pc AA Battery
Note:This product is a material package, it needs to be made by yourself.

This is a science experiment diy kit with a very simple assembly process
1. Insert the two iron shafts into the holes of the reduction motor, and then put on the red case.
2. Put two semi-circular EVA on the red case.
3. Glue the round EVA to the bottom of the motor(place the glue side up).
4. Attach the accessory "eyes" to the EVA's eye frame, then attach it to the motor with double-sided tape (accessory "eyes" with glue).
5. Connect the wire with the battery holder and then connect the motor.
6. Attach double-sided tape to the switch and battery holder,  then attach it to the motor.
7. Install the wooden stick and battery.
Note: The small stick should be installed at the front end to prevent loss of balance and unstable walking!