The curious case of the cross eyed cartoon characters

It's amazing that so many people in Anime. It is especially common in Pokemon but it is by no means limited to that show. I observed in many other animes having certain characters (especially heroes) being cross eyed. Why are there so many cross eyed people was there once a great Japanese hero who was cross eyed and therefore in Japanese cartoons it is associated with heroism? If somebody knows the reason please post.