mmm, I doubt this. Toilets are in the pressurized area of the airplane, and that area is sealed from the outside. I can only think of the outflow valves (which are small on most airplanes and are a high jump to reach from ground), and via doors which give access to baggage compt or avx compt. But in this case, the aircraft has to be on the ground or you can't open the hatch due to pressure.