The character known as Bull, often referred to as Laughing Bull, is a minor but significant figure in the narrative. He is a nomadic Native American living on Mars with his son. A shaman or holy man, he practices traditional customs and offers guidance to those who seek him out, though his advice is often cryptic and metaphorical, making it difficult for outsiders to immediately understand.

His background is one of a traditionalist living in a futuristic, technologically advanced society, as evidenced by his home being a tent located near a junkyard, yet also containing modern items such as a PlayStation console. His appearance and role are visually inspired by historical Native American figures like Sitting Bull.

Bull's personality is calm, wise, and spiritual. He speaks in riddles and uses symbolic language, referring to the bounty hunter Spike Spiegel as Swimming Bird and his partner Jet Black as Running Rock. His motivations are not driven by personal gain but by a desire to observe the flow of life and death and to impart his wisdom when he feels it is necessary. He serves as a spiritual anchor, representing a connection to ancient traditions and a cosmic perspective on the events unfolding around the main characters.

In the story, Bull acts as an oracle and a helper. He is first sought out by Spike to help track down a drug dealer named Asimov Solensan. Using his spiritual insight, Bull correctly predicts where the red-eyed coyote, referring to the target, will appear. Later, while sitting with his son, he observes a shooting star, which he interprets as the tear of a warrior, a lost soul who has finished his battles but cannot find his way to the great spirit. In the feature film, after Spike is severely wounded in a fight and falls into a river, Bull finds him, pulls him from the water, and tends to his injuries. During this time, he provides Spike with crucial philosophical counsel, referring to Spike's two different eyes and calling one the eye of truth, telling him he has nothing to fear from death.

His most pivotal role comes near the end of the series. When Spike leaves to confront his past, Jet visits Bull to ask where Spike has gone. Bull explains to Jet that every living creature has a guardian star that falls when the creature dies. He then foretells that Spike's star is about to fade, preparing Jet for the impending loss while again advising him not to fear death. This prophecy is visually reinforced in the series finale when a star is shown twinkling and then fading out.

Key relationships for Bull include his young son, to whom he imparts his wisdom and observations about the world. He also has a recurring connection with Spike and Jet, who, despite their own skepticism, respect his knowledge and seek his counsel in times of need.

The character does not undergo significant development, as he serves as a static, wise figure whose purpose is to guide others. His role is to observe and interpret the spiritual ramifications of the characters' violent journeys. His notable abilities are not physical but spiritual and intellectual. He possesses a form of foresight or prophecy, allowing him to predict future events and the fates of individuals. His wisdom provides both practical information, like a target's location, and deep philosophical insight into the nature of life, death, and destiny.