King Dedede proclaims himself ruler of Dream Land from his castle overlooking Cappy Town. His authority is mostly nominal, performing no administrative duties while townspeople routinely ignore his edicts. He maintains his title through intimidation and occasional displays of force, leveraging his wealth to impose his will. His background before claiming rulership remains largely unexplored, though he appointed Escargoon as his assistant and enforcer at some point.

Dedede exhibits a consistently greedy, lazy, and self-absorbed personality, prioritizing his own desires—especially food and leisure—over his subjects' welfare. He harbors intense jealousy toward Kirby, viewing the Star Warrior's arrival as a threat to his status. This rivalry drives him to repeatedly order monsters from Nightmare Enterprises to eliminate Kirby, famously demanding, "I need a monster to clobber that there Kirby!" during each transaction. These monsters often inadvertently endanger Cappy Town's residents, reflecting Dedede's disregard for collateral damage.

His relationship with Escargoon is complex; Dedede frequently bullies and belittles him, yet Escargoon remains loyal, often participating in schemes seeking approval. Dedede also employs Meta Knight and Captain Waddle Doo, though their allegiance is conditional and occasionally conflicts with his goals. Despite his antagonistic role, Dedede displays rare moments of compassion. He honored a promise to build a playground for children despite an impending asteroid strike and exhibited genuine grief during a staged funeral for Kirby, crying at the gravesite before expressing relief upon discovering the deception.

Dedede's character undergoes partial development. After Nightmare Enterprises betrays him, he allies with Kirby and Meta Knight to confront the true antagonist, eNeMeE. In the finale, he participates in the battle against eNeMeE, contributing to the corporation's downfall. Post-victory, he loses access to monster procurement, symbolized by his futile attempt to use a defunct customer service phone. Later appearances suggest reduced overt malice, though his core traits of self-interest and impulsiveness persist.

Memorable aspects include his comedic ineptitude, exaggerated tantrums upon defeat, and quotable lines gaining cultural traction among fans. His dynamic with Kirby evolves from one-sided hostility to reluctant cooperation, though he never fully abandons his opportunistic nature.