Well, I did one complete two-step cycle with bone animation and repeated that while using layer translation
So:
- bone animation left step (frames 1-4)
- bone animation right step (frames 5-8 )
- quick layer translation (frame 8/9)
- bone animation in frames 9-16 is the same as in frames 1-8
- quick layer translation (frame 16/17)
- bone animation in frames 17-24 is the same as in frames 1-8
- quick layer translation (frame 24/25)
etc.
Now, a cat never walks in a straight path, at least, not in slow walks, so you need the cat to move on a curved path instead of a straight line. You can do the following to move your 2D layer (or group) in 3D along a path:
1) create an image of a tile floor, like this 640 x 480 PNG image:

2) import it into MOHO with a 320 x 240 format
3) move it so, that the bottom of the image aligns with the bottom of the visible area (1 unit up vertically)
4) move the center to the bottom of the visible area (2 units down vertically)
5) rotate the image layer -90 degrees around the x axis
Now everything you draw in a vector layer that is within the visible area will be either on or above the floor. And if you move that vector layer into the negative z or both x directions, you move the drawn objects either on or above the floor.
Now you can draw a walkpath on the floor very easily, by using the tiles as a reference. Simply do the same operations 3-5 on a vector layer and draw in that vector layer.
Here is a simple animation of a rectangle moving on the floor.
http://media.putfile.com/Walk-the-path-76
Of course, your 2D animation should reflect the movement in 3D. You could use two or more 2D layers for the torso, and one (or more) for each limb. Now your cat can move its torso in 3D by rotating the torso layers along the x and y axes. Make sure you put the layer center at the correct position (because it acts as the pivot point for the rotation). Something similar applies to the limbs, the head and the tail.
Selgin had made an example of this technique (African Elephant), but the video has been removed from YouTube, so I can't point you to that animation example.