Big Boy was struggling to put his shopping in the car through the pouring rain.
In the storm, he was hit by a lighting bolt and was sent to the hospital, where he met Doctor Marvin. Marvin said that Big Boy had been hit in the brain by the lighting and that his brains had 100 times the normal of electrons running through his brain allowing him to think 100 times faster than anyone else.
The next day, when Big Boy was at McDonalds, 2 ladies were abusing a fat person, so big boy stepped in and tried to break it up. One of the girls tried to hit him, but he saw it coming before she had even started moving her hand and he dodged it. They were then humiliated and they walked out. That was when he realised he was a big boy, so he named himself 'Captain Big Boy.'