In the first episodes he uses the kyuubi chackra for the mass clones technique. Later on he improves his chackra by hard training, and he was born with an unusually high amount of chackra.<br/><br/>And the explanation Kakashi gave was quite plausible to accept it as reasonable the increase in the learning speed for the rasenshuriken.<br/><br/>Luffy rocks! He is a complete idiot but still a genius in his idiocy. They have a tight group that became partners by respecting each others powers. On the other hand Naruto and the others were just jumbled together and so far everyone is drawn to him and not quite the other way around.<br/><br/>Still in One Piece they come up with techniques they knew but didn't used before, eventhough they were about to be killed or nearly death.