Board Thread:General Discussion/@comment-44061-20130307153642/@comment-2211792-20130308094334

The Super Hollow form was actually foreshadowed by Hichigo ("when one is dominated by life, he is flesh; when one is dominated by death, he becomes bones" or something along those lines), not to mention him always saying that if Ichigo dies, it'll be a problem for him. Also, Hichigo is his instinct personified. So when Ulquiorra killed Ichigo for the second time and Orihime was calling for help, his deepest desire to protect and destroy awakened, and Hichigo emerged at full power. Plus, there's also the fact Ichigo is stronger than the Visoreds because they are, in Aizen's words, "failed mock arrancars". His experiments on Shinji and others were only a partial success; somehow, Urahara's Shattered Shaft method proved better.