Danny

Background

Danny was a pet mouse kept by Johnny Joestar when he was around nine years old in 1881 while living in England. His father, George Joestar, only allowed Johnny to keep Danny if he was inside a cage at all times. During a family dinner, Johnny secretly fed Danny scraps of meat under the table, hiding Danny in his jacket's pocket. George caught Johnny and was furious that he brought a rodent to the table, citing it as poor manners for a Joestar.↗

Distraught, Johnny ran outside but could not bring himself to kill Danny. His older brother, Nicholas Joestar, found him crying. Nicholas came up with a plan to save the mouse, suggesting they release Danny into the forest to live freely. To appease their father, Nicholas proposed that Johnny ask his teacher for a taxidermy white mouse the next day to present to George as "proof" that the deed was done. Grateful for his brother's help, Johnny released Danny into the woods.↗

Some time later, Nicholas was practicing on the race track with a temperamental horse named Black Rose. As Johnny timed the lap, the horse was suddenly startled and threw Nicholas off. Diego Brando claimed that a white mouse suddenly scurried past Black Rose's feet and then ran off into the woods. Johnny became convinced it was Danny. He blamed himself for his brother's death, believing that his failure to drown Danny directly led to the accident.↗↗

Steel Ball Run

About nine years later, during the Steel Ball Run, mice resembling Danny appear during pivotal moments involving Johnny. When Johnny discovers the Golden Rectangle in nature, he spots a white mouse and calls out Danny's name before evolving Tusk to ACT2.↗↗

During the fight against Axl RO and his Stand Civil War, Danny reappears as a physical manifestation of Johnny's past sins. The mouse manifests in front of Johnny and charges toward him. Since Civil War's ability brings back the "trash" one has thrown away, the guilt of releasing Danny and believing he killed Nicholas returns to haunt Johnny. The mouse proves difficult to hit, dodging Tusk's nail bullets.↗

A manifestation of Nicholas emerges from the boot instead and covers Johnny with a membrane, while the fake Danny scurries toward Johnny. Johnny attempts to cleanse himself of his "sins" using water to get rid of the Stand. The fake Danny leaps toward his arm, covering his face and upper torso with the membrane. However, Johnny shoots his canteen of water that Slow Dancer was carrying and lets the water splash on himself, melting the membrane off him.↗↗↗

Later, Funny Valentine is momentarily distracted from finishing Johnny off by a white mouse resembling Danny rustling in the grass behind Johnny. Valentine suspects the mouse was pulled there by D4C Love Train 's misfortune redirection, before he is pulled away from Johnny due to Lucy Steel being moved by Steven Steel. When Valentine tells Johnny about his father, Johnny thinks about his own father as well as Danny.↗↗↗↗