Arthur, formerly known as the unnamed_old_deer, is a character created alongside Sino on July 22nd, 2010 by the artist Furfragged. He was given the name Arthur in a fanfiction written by fullbloodedlion on January 6th, 2019. This name was later accepted by furfragged on December 25th, 2019 as the character's canon name.

Arthur is an older anthropomorphic stag, at least past his 60's due to the existence of a buff_middle_aged_deer. Arthur is usually depicted in monochromatic sketches, but appearance wise, Arthur is an portly older deer, he has dark brown fur, with a beer belly, who usually wears a black t-shirt or an orange tank top and occasionally a leather harness. Otherwise, he is completely nude. Arthur is frequently depicted in a series of pseudo video game overs in which he usually takes on an antagonistic/enemy role. He usually confronts horny Sino and seduces the latter, leading to a game over.

In recent years, Arthur is generally considered to be Sino's consensual lover and canon romantic interest. Occasionally, he fails to seduce Sino or seduces another younger male.