Once upon a time Nidoking was sleeping in his seashell and his dad barged in drunk and nude saying, "Where's my asswipe?!" after which he fainted loudly on his desk. Nidoking turned to his bed partner Swinub and apologised for his father's behaviour. That wasn't enough though, and Swinub packed his things and left. This made Nidoking heartbroken. He got dressed up for work at the textile factory but, halfway there, a UFO came out of nowhere and lit an intense light beam at him and abducted him. He woke up strapped to a table as unfamiliar beings leaned over him, observing his every move. He begged for them to let him go, but it all seemed in vain because they could not utter his language, let alone hear it. After some time passed, they activated a loud machine near him, and he felt something insert itself up his anus. Of course, he got aroused from it, and the beings examined his member. They injected him with some substance and he quickly fell asleep, only to wake up naked in the middle of the desert with his memories gone. His first instinct was to rub himself against a cactus, something he dreamt of since his childhood. Luckily, he found dick boxers on the cactus, so he put them on. After walking for some thirty minutes, he found a group of Pokemon wrestling in mud to find out who would win a copy of the new Killer Instinct game. Being a big fan, he decided to join the contest, and he was immediately pitted against Machoke. Then, Scrafty. Then, Dragonite. And Larvitar. They couldn't believe how strong he was, but little did they know, as his strength came from his underwear. Then, he faced off against Rhydon, the one who hosted the contest. Rhydon, however, wore underwear of the same kind as Nidoking - infused with power beyond comprehension. The fight was intense, but seemed trivial, as their powers were matched, practically cancelling one another. The strain was so great that Nidoking's underwear began to wear out. The power that coursed through the minuscule fibres quickly became unstable and escaped to his body - or more specifically, his genitals. That power was too great to contain, however, and as Nidoking's dick became erect it further put strain on his underwear, which in turn liberated more energy on Nidoking's dick. All of this happened within a few seconds, and Nidoking's dick tore through his underwear, and he began ejaculating strongly.

That's the digested version. Find my series of 17 books depicting Nidoking's trials and tribulations in your nearby bookstore. There's three whole books revolving around the underwear and how they came to be.
Coming out never. :v