I Am Trying To Make A Panther

I am trying to make a panther sized robot ( about 3 feet high, 4 feet long and 1 1/2 foot wide). I would like it to be a fast robot, since it is for my schools pep-rally's, I am thinking wheels, but I would still like the legs to move. I would like to be able to be a little weather proof, since it will send some time outside, and also be able to take on grassy terrain. Lastly, i would like it to be not too heavy for easy transportation.