As a boy, Keroppi was a smart, studious frog. Keroppi and his brother, Koroppi, were the smart ones of Donut Pond, always envied by the other kids of the city. Keroppi was even a bit of an overachiever, taking swimming and singing lessons in his spare time. Their father, Keroppa, had very high hopes for the boys. He is praised across the globe as the world's most brilliant doctor and surgeon. Keroppa is believed to be able to cure any illness or ailment, and it was his belief that these boys could surpass even him.
Pikki isn't exactly on the academic level of Keroppi and Koroppi, but she's still a very intelligent girl. More importantly, she is hot. I mean, wow! This isn't about that, though. Like the boys take after their father, Pikki takes after their mother, Keroma. She is training to be a master chef and take over the family restaurant, and she has already earned the love of the locals for her masterwork: Kerocakes. They're pancakes, but with more kero.
Unfortunately for Pikki, it turns out that the Kerocake recipe isn't a Kerokero Family creation, as Keroma claimed. The Kerokero Family's American rivals, the trio known as "Boo Gey Woo" created the Kerocakes to bring the taste of Donut Pond to the American Southwest. Keroppi's grandparents, Kerojee and Kerobah, knew instantly that this was infringing on their Kerokero trademark, but also knew that a drawn out court case over the Kerocakes would harm their reputation in the long run. They took matters into their own hands and hired Furui Badtz-Maru, grandfather of Badtz-Maru, to steal the Kerocakes recipe from the Boo Gey Woo trio, so the Kerokero Family could make it their own.
Now, two generations later, the Boo Gey Woo trio have made the presence known once more: They kidnapped Pikki, and have taken back the Kerocakes recipe. The Kerokero Family keeps the reasons for Pikki's kidnapping a secret, to prevent the locals from discovering the truth and ruining their family business. Moreover, it would ruin Keroppa's reputation as a respectable doctor, something that could rock the very foundation of the world, heralding a resurgence of disease and death.
Keroppi, unable to tolerate the growing hopelessness of the situation, gathers two unlikely heroes from Donut Pond: Kyorosuke, an amazingly tall frog blessed with incredible vision, and Ganta, a short but powerful frog with the ability to turn himself into a rock. Together, these three form the Ganta-Kyorosuke-Keroppi Gang. United, the three of them acted against the Boo Gey Woo trio from the shadows, thwarting many attempts made by the BGW to dominate and control the culinary world, building up to one final battle to retrieve Pikki and restore the Kerokero Family's rightful place as Iron Chefs.
It took nearly a year to meet Keroppi's ultimate goal. Ganta, Kyorosuke and Keroppi reached the American Southwest to finally face down the Boo Gey Woo, and the battle was horrifying. The BGW were ruthless, using anything and everything for an edge, including threatening the death of poor Pikki. Ganta, ever-brave, called the pig trio's bluff. Boo Gey Woo weren't to be toyed with, and did not hesitate to make the most of this opportunity. Together, they turned to strike at the beautiful young frogwoman, but Keroppi would have none of that. With a great shout which caused the ground itself to tremble, Keroppi summoned up every ounce of qi in his body and called up an ancient power held within the Kerokero Family: The Kage Bunshin no Jutsu. Keroppi hopped with such speed and strength that one frog seemed to be ten! Then twenty! Fourty! One hundred frogs! The Boo Gey Woo ran in fear, and Pikki was saved.
Keroppi, Ganta and Kyorosuke returned to Donut Pond with the city's beloved Pikki, who was welcomed with open arms. Unfortunately for the Ganta-Kyorosuke-Keroppi Gang, during their crusade against the Boo Gey Woo, they were expelled from school due to extended absences. The Kerokero Family, considering this a black mark on their reputation, exiled Keroppi from the family and have worked since then to remove him from this history entirely.
Keroppi, disgusted with the power of reputation and society at large, has since departed Pond Lake and has taken up residence on an offshore island. His allies, Ganta and Kyorosuke, have remained on the mainland to siphon funds from the defeated Boo Gey Woo's bank accounts illegally, redirecting the money to Keroppi. Keroppi has begun using these funds to research methods of growing super sized lily pads, which he intends to use to crush Donut Pond, thus beginning a new world. A world with all of the joys of this one, and none of the hatreds. A world of equality, where the Kerokero Family will be reborn and live in peace.
This is where Hello Kitty Online began, and rumor has it that Keroppi and the next chapter of his story will be the focus of Hello Kitty Island Adventures alongside Badtz-Maru, grandson of the man who stole the Kerocakes recipe, and they will be the final bosses of the expansion. Better round up 24 of your closest friends, I'm willing to bet Keroppi's pinks will be truly amazing. Remember, watch out for his Kage Bunshin!