Mordecai has tuxedo colored fur and olive green eyes, he has short hair at the top of his head that droops down and wears rounded pince-nez. He commonly wears the Marigold uniform with a red tie but occasionally wears a long, black coat with a beige fedora or a white-collared shirt with suspender pants. Serafine forcibly carved a Voodoo protection glyph into Mordecai's chest when he refused to join the Maitre Carrefour cult.[2] Due to this in some comics he has a blood stain in that area. According to a QNA page about eyebrows, Mordecai’s were styled so he would always look mad.

Mordecai was born on March 28, 1899 in New York City, New York to German-Jewish immigrants. Before starting education, Mordecai suffered from congenital myopia and was forced to wear spectacles. After his father Issac passed from a stroke, Mordecai became very protective of his family when they moved to the east side of Manhattan in terrible living conditions. He only finished his primary education.

At 13, Mordecai began working as an accountant and bookie for grifters, loan sharks and gambling operations. In need of money at 17, he extorted money from someone minor in the crime world, murdering them as he replaced their role and was able to embezzle money from higher ranks, though he was later caught.

In fright, Mordecai gets on a getaway train to either Chicago or Detroit while leaving all his money for his family; however, while finishing a letter to his mother explaining the situation, he notices two thugs in the traincar watching him, and realizes he is being pursued. While Mordecai is asking around for a stamp, the train enters a tunnel before Atlas appears from the shadow, coming to sit on the other side. He and Mordecai exchanged glances briefly before Atlas stood up to leave for his destination, all the while leaving a revolver inside the newspaper that he carried onto the train. Mordecai took the revolver and used it to defend himself and escape from his pursuers.

Atlas helps Mordecai get out of his former troubles and Mordecai decides to join Lackadaisy as a sharpshooter. Though, after Atlas' death in 1926, Mordecai got into a fight with Viktor and eventually kneecapped him. He was later hired by Asa Sweet in early 1927 to be a triggerman for Marigold.

Mordecai was shown as reserved and professional in nature with a likeness for cleanliness and order. He seems to have a dislike for touch which was shown when he avoided Ivy in the episode Ingenue and when requested to dance in the comic; he also became visibly uncomfortable when Gracie put his hand on Mordecai's shoulder in a friendly gesture. He worked to keep an intimidating persona as an triggerman albeit became awkward if it did not work as intended. Mordecai was shown as a perfectionist, wanting symmetry and having his Earl Gray tea a specific amount of time.

(Mordecai is your Father in this AU)