For instance, did you know that the periodic red hadoukens in Street Fighter 2 were not glitches, but instead easter eggs that became wildly popular among fans? Or that each pugilist was originally supposed to feature positional damaging - kicking someone in the head would do more damage than kicking them in the leg - but that the feature was cut because the game just refused to recognize hitboxes properly?
My favorite bit of trivia is the controversy over Chun Li's leggings. The development team was okay with Chun Li's borderline-equine thighs, but the tights covering them were a massive point of contention. According to Nishitani, they had to be redrawn from scratch three times before Capcom finally agreed to the outfit.
More insider information on the creation of the world's most influential fighting game can be found on Akira Nishitani's Twitter account. If you don't read Japanese however, Eventhubs offers an extensive roundup.