Casey Jones first appeared in the 1985 comic Raphael: Teenage Mutant Ninja Turtle.
The one-shot comic introduced Casey as a masked vigilante who fights criminals with sports equipment, including hockey sticks, baseball bats, and cricket bats. His exaggerated arsenal and homemade approach distinguish him from the turtles, who use traditional ninja weapons. He soon became one of the franchise’s most recognizable human allies.
Casey’s relationship with April O'Neil and the turtles varies between adaptations, but he is commonly portrayed as courageous, impulsive, and highly committed to street justice. The 1990 film made him a central supporting character, played by Elias Koteas.
The character’s first appearance is sometimes misidentified as an issue of the main ongoing Teenage Mutant Ninja Turtles series. It was actually the Raphael-focused one-shot, published by Mirage Studios in 1985. Later cartoons, comics, and films adapted his visual design and vigilante identity in different ways.