Oslo, once reigning as the King of All Food, was overthrown when his student Chef George, the future King Gorgeous Gorge, betrayed him. This betrayal condemned Oslo to exist as a diminutive man who relied entirely on a floating saucer for mobility, stripped of his former stature and power. His magical abilities, drastically reduced, concentrated within the distinctive swirling vortex of hair atop his head, serving as the core reservoir of his remaining strength.

Following his fall, Oslo joined the rebel chefs fighting King Gorge's Glutton Empire. He emerged as a pivotal mentor, having previously trained the rebellion's leader, Chef Jack. Later, he shouldered the duty of training Jack's son, Chase, honing the boy's culinary and combat skills to forge him into a Master Chef capable of challenging the empire. Oslo guided Chase throughout his journey, gifting him his first magical Meal Ticket—cards used to animate food into Fighting Foodons—after Chase rescued him from peril. His mentorship often employed unconventional methods, like using placebos such as a "turbo-powered" Meal Ticket to bolster Chase's confidence.

Oslo forged connections with the underground Hot Peppers resistance network, collaborating with members like Jambalydia to aid victims of the Gluttons. Despite his wisdom, he frequently provided comic relief through his eccentric personality and occasional magical blunders. His arcane knowledge proved vital during the final clash with King Gorge. When Gorge unleashed Devouron, an embodiment of evil fueled by the Dark Nebula's power, Oslo channeled his magic to enable Chase and his Foodons to unite into Palator, the embodiment of good. This act destroyed Devouron, defeated Gorge, and cleansed him of evil.

After the conflict, Oslo shifted his focus to supporting reconstruction efforts.