These are the legos you'll need. Some substitutions may also work. :). The second picture shows Legos you'll need to make legs.
Let's do it Lego Style
Add this to that
That's one rubber band on a plate, and you can put the 1x2 on the left or the right, depending on which way your battery faces.
Make A Circuit and a Rectangle
The circuit is power + light sensor (light) + tethered DC motor. Put this circuit on the type of Brick Adapter shown. Complete the Lego rectangle shape, and add plates to the Kitchen Bot - let's call them chest plates.
Press the Brick Adapter and circuit
Take care to only press on Legos, Brick Adapters and the colorful bitSnaps on littleBits. Never push or pull on littleBits' white circuit boards. String the tethered DC motor between the top of the chest plates and the top of the Lego rectangle.
Put the motor on back
Press the tethered DC motor into the other type of Brick Adapter and then onto the back of the chest plates. Again, take care to press on bitSnaps, but not circuit boards.
Make two sets of these legs as mirror images.
Gear up & Add back plates
Push the axle through crankshafts at the fourth hole from the bottom on our Lego rectangle. Place the crankshafts at opposite angles for an alternating step motion. Get a crown gear in there, too. :) Push the other gear onto a short axle and attach to the tethered DC motor with a motor mate. Adjust until the gears mesh, and press back plates against the plastic motor body. More back plates will increase stability. Keeping the gears meshed is the most difficult part, which will require a lot of adjustments.