Marquess was born on July 20, 1844.
As common among stereotypical ghosts, Marquess' attire, complexion, and hair color and completely white. Having been born in the nineteenth century, Marquess dresses very formally, always dressed in a suit and top hat. He is tall with a lean, but well-built physique, along with glasses and a mustache.
Marquess is perhaps the most honest, polite, courteous, well-mannered and compassionate member of the Mystery Team. Marquess is also homosexual and very effeminate, in addition to being easily anxious, agitated and somewhat cowardly is stressful situations.
Marquess could be considered the antithesis to Pigeon: Marquess is proper, polite, and considerate of others, while Pigeon is vulgar, rude, sarcastic and enjoys mocking others and making crude jokes. As a result of their contradicting personalities, Marquess is frequently a target of Pigeon's sarcastic and sadistic jokes, which involve mocking him for his sexuality and effeminate interests.
Marquess has demonstrated numerous unhealthy habits, including chain-smoking cigarettes and alchoholism, which he has failed to overcome and is very self-conscience about.
- He is Jewish.
- He is the ghost of John Douglas, 9th Marquess of Queensberry.
- The Marquess portion of his name is pronounced "Marcus" and rendered as if it is his actual name, instead of a title.
- It is revealed in "My Favorite Mystery", that Marquess has claustrophobia.