Tweedle Dum forms half of the twin gatekeepers enforcing the Hatter Mafia’s authority within their territory, partnered inseparably with his brother Tweedle Dee. In their childlike forms, they mirror each other in almost every aspect, save for Dum’s crimson irises and red-trimmed attire, opposing Dee’s blue-accented features. As adults, Dum’s hair shortens, pinned with black-and-red barrettes, while Dee favors longer locks secured by a blue ribbon. Their demeanor oscillates between playful mischief and calculated brutality, favoring axes over firearms for the visceral thrill they provide. Though prone to mocking insults and erratic violence, they harbor a warped innocence, directing unwavering loyalty solely toward Alice—whom they affectionately call "Onee-san" in any age form.

The twins operate as a fused entity, sharing romantic interests and a collective identity, yet retaining trivial individual preferences in flavors or colors. Within the Country of Diamonds, they permanently adopt adult forms, masquerading as abrasive salarymen fixated on workplace perks and vacation days. Initially distrustful of Alice, accusing her of espionage, they later exploit her generosity for sweets and leisure, growing fiercely possessive if she engages with others.

Their dynamic shifts when suspicion morphs into infatuation. A marriage proposal follows, orchestrated with Blood Dupre’s aid, who gifts them a shared mansion with Alice. Though protective, their impulsivity persists—threatening intruders at the gates with lethal force. Cohabitation tightens their scrutiny over Alice’s life, blending obsessive guardianship with volatile affection.

Behind their chaotic facade lie ineptitude in cooking and a knack for biting sarcasm. As the sole adult twins in the Diamond Country’s timeline, their role under Blood Dupre involves gatekeeping and combat in territorial disputes. Spin-off narratives depict coerced participation in sabotage missions, torn between mafia orders and flickering moral hesitations. Their joint ability, "Windstoß," manipulates energy fields, though they depend on allies for intricate tasks. Acts like containing geo-sort-bombs at personal risk hint at buried nobility beneath their anarchic exterior, while mutual sacrifices in battle or tentative hopes for peace reveal fleeting vulnerability beneath their destructive whims.