There once was a mean little boy named Mitch. His body was full of bad little particles. He would dunk over all of the kids in his class, and he would laugh in their small ugly faces.
One day, he dunked over Radiation Boy, and Radiation Boy cried and cried because he had been owned at basketball. He cried alpha particles, beta particles (electrons), and gamma rays. Much radiation came spilling out of his body and into the body of Mitch.
These radioactive particles fixed on to all the bad little particles that were floating around inside of the young boy, Mitch. They made the bad particles so heavy that they sank down from his head, through his neck, past his torso and groin, down through his legs, and into his feet. They went through his ankles, past his heels, along his metatarsals, through his phalanges, until, finally, they all collected in his toenails. There was no more badness in the rest of his body.
That's how Mitch came to be a great guy with awful toenails.