Antonio is one-third of a trio of elderly, recurring background characters in Cowboy Bebop, alongside his two constant companions, Carlos and Jobim. The three men are almost always seen together, typically seated at a table in a restaurant, diner, or bar, often in the middle of a card game. They appear in many episodes as the crew of the Bebop visits various locations across the solar system, functioning as a running gag where they happen to be present at the same establishments as the main characters, though neither group ever acknowledges having met before.

In terms of personality, Antonio is portrayed as the most outspoken and easily frustrated member of the group. He has a short temper, particularly when it comes to money, and is not afraid to voice his displeasure. In one instance, he angrily accuses Carlos and Jobim of cheating him out of his cash, declaring that the only reason they can afford to eat is because of his own hard work planting crops alongside them. This complaint highlights a sense of shared history and labor, as the trio claims to have dug the Astral Gate together, a monumental engineering project that hints at a long and rugged past. Despite his bickering, he remains a steadfast member of the group, and their frequent arguments are presented as a familiar and almost comfortable ritual of their friendship.

The role of Antonio and his friends in the story is primarily that of comic relief and a narrative device. Their conversations, often about trivial or financial matters, frequently echo the central themes or key plot points of the episode in which they appear, acting as a sort of humorous Greek chorus. They are not involved in the main action but serve as a familiar, grounding presence within the universe, appearing as background fixtures in the lives of bounty hunters and other characters. Their most prominent deviation from this background role occurs in the theatrical film, where the trio is seen piloting one of the planes distributing a vaccine.

Antonio does not undergo any significant character development throughout the series, as his function is to provide consistency and color to the world rather than to drive the plot. His motivations are simple and grounded, typically revolving around winning his card game, enjoying a meal, or complaining about his finances. His key relationships are exclusively with Carlos and Jobim; their dynamic is the core of his identity as a character, and they are rarely, if ever, seen apart.

Regarding notable abilities, Antonio possesses no special combat or technical skills relevant to the main storyline. His primary attributes are his persistence and his ubiquity, seemingly able to appear at random locations across the solar system. The very name Antonio, along with Carlos and Jobim, is a direct reference to the legendary Brazilian musician Antonio Carlos Jobim, a foundational figure of bossa nova music, reflecting director Shinichiro Watanabe's well-known appreciation for jazz and its related genres.