Mister Boobrie is a small bird-like creature with lime-green skin, a beige beak, and two small beige-tinted ram horns curling twice. Dark blue bat-like wings emerge from his back. He typically accompanies the sorceress Mélie, often riding nestled within or perched atop her massive hair.

In his typical state, Mister Boobrie snaps with a volatile, aggressive, and unforgiving nature, acting as the direct antithesis to Mélie's cheerful demeanor. His temper particularly sours during joyous occasions, often driving him to peck or bite his owner. He displays fierce fearlessness in confrontations, even defeating a cat in combat. However, his personality undergoes a complete reversal when Mélie's curse activates; he becomes submissive, affectionate, and desperately attention-seeking while actively avoiding conflict. This drastic shift is directly tied to Mélie's Persona Switch curse, forcing his state of mind to always oppose hers.

During the Pompo Hills incident, Mister Boobrie evaded the Inquisition following Mélie's arrest. He stealthily retrieved keys to free her, Seth, and Doc from their cages. Later, he and Mélie were mistakenly recaptured by the Inquisition due to superficial similarities—his horns caused confusion with Seth, while Mélie's hair resembled Alma's. They remained imprisoned for three days until Seth intervened.

Despite his diminutive size, Mister Boobrie wields surprising strength, capable of supporting the weight of teenagers. His wings grant him notable flight endurance, and he exhibits exceptional stealth and craftiness, such as swiping keys unnoticed. His inherent combativeness starkly contrasts with his conflict avoidance during Mélie's cursed episodes.

The character consistently functions as Mélie's companion across appearances, with no significant evolution in background or role beyond the established traits and plot contributions. His actions primarily facilitate escapes or complicate situations through mistaken identity, without broader development in later arcs.