Bulldog, alternately called Bull or Biff, is one of two relentless troublemaker brothers dedicated to sabotaging the protagonist and friends. Their chief objective centers on antagonizing Baby Felix, particularly when he relaxes or bonds with Baby Kitty. Schemes like rigged prank-traps provoke clashes, often triggering Baby Felix’s retaliatory magic bag tricks—such as melting their ice cream, which backfires on the kitten with unintended punishments.

Though Baby Felix occasionally aids them, like extinguishing a house fire with his magic, their hostility persists. They dismiss such help, accusing him of collateral mishaps instead of showing gratitude. Their rivalry cycles through petty disruptions and fleeting confrontations, sustaining a pattern of friction without growth or reconciliation. Motives remain rooted in trivial mischief, cementing their role as foils to Baby Felix’s cheerful, earnest demeanor. No additional context about their origins or relationships beyond this dynamic is documented.