You must not know many ninjas from our world. Many ninjas can carry sacks of large sizes, and in fact it becomes more understandable that he could fit presents for so many people into one sack if you consider a ninja's summoning arts. Additionally, one of the greatest ninjas whom I know is Naruto-kun, who wears all orange! He seeks to become Hokage one day... if he succeeds, it is easy to imagine him being much like Santa-sama when he reaches old age!