Casey Jones (TMNT 2003)

Casey Jones is a hockey-masked self-titled vigilante who fights crime at night and a close friend of the Ninja Turtles (mainly Raphael), as well as the later husband of April O'Neil.

History
Raphael first meets Casey while the vigilante tries to stop a mugging by the Purple Dragons. Seeing a lot of himself in Casey, Raphael tries to reason with him and prevent him from letting his anger get the best of him (Raphael himself had just almost severely injured Michelangelo and was overwhelmed by guilt). Though initially uninterested in what he has to say, Casey eventually bonds with Raphael after he loses to Raph in a bike race and begins listening to his lessons. Casey, Raphael, and the other turtles proceed to team up and defeat a gang of Purple Dragons. From this point on, Casey becomes a valuable ally of the Turtles, and has a closer friendship with Raphael than in any other incarnation.

Casey's backstory is fleshed out over the course of the series. When he was a child, his father's shop was burned down by Hun and the Purple Dragons for being denied protection money. Despite being threatened not to, his father (Arnold Casey Jones Sr.) later went to the police over it. It is implied that he was killed for doing so. This gave Casey his hatred for crime and an essential lifelong vendetta against the Purple Dragons.

It is revealed in episode "The Lesson" that he and the Turtles had met when they were kids, although neither the Turtles nor Casey are aware of the truth. During a trip to the surface, the young Turtles witness bullies picking on young "Arnie". Disguising themselves as a human child, they attempt to teach him self-defense. However, their unique perspectives and attitudes resulted in more trouble than help. In the end, however, young Casey angrily jumps to the defense of a friend against the bullies, proclaiming they were no match for "Arnold Casey Jones!" In a bit of foreshadowing, he uses a bully's hockey stick against them.

His main catchphrase is the battle cry "Goongala!". It is also revealed in "The Lesson" that this came from a young Casey being unable to pronounce "gorogoro-sama", a battle cry literally meaning "Mr. Thunder", that young Michelangelo kept trying to teach him. "Goongala" was the best he could come up with.

Despite his lack of intelligence and apparent incompetence, he was early on in the series referred to by Hun as "Our (the Purple Dragon's) greatest enemy", and a fighting tournament was held to see which Dragon would have the honor of killing him, indicating how serious a threat the criminal underworld views him as.

In the series, Casey has a good heart, but is easily enraged and occasionally bumbling. He loves motorcycles. In a symbolic way, he sees the Turtles as the little brothers he never had. As such, he often comes to their aid against the Shredder, the Foot Clan, or other enemies.

Early on, Casey meets April and there is an initial attraction. However, their conflicting personalities lead to frequent arguments at first. Over time, however, they start dating and a serious relationship develops. In the Back to the Sewers (seventh) season, Casey proposes marriage to her. In the finale "Wedding Bells and Bytes", they are married, with Raphael serving as the best man and Michelangelo as the maid of honor. Many recurring characters were in attendance and the ceremony performed by the Fugitoid. In the Fast Forward (sixth) season, the Turtles and Splinter are transported to 2105, where they meet April and Casey's great grandson, Cody Jones, the heir to O'Neil Tech, a company created by April, Casey and Donatello after the turtles return to their own time. One of Cody's inventions, the Turtle X armor, resembles Casey's hockey mask.

Trivia

 * He has a farm in the countryside left to him by his grandmother.
 * In the 13th episode of season 3, "The Lesson", Casey's modern-day battlecry originated from Michelangelo, who taught him to shout "Goro Goro Sama!" (literally, "Mr. Thunder"), which Casey ultimately garbled into "Goongala!"
 * Casey's favorite food has been stated to be Italian, Mexican, and pretzels.
 * Casey's favorite color is green.
 * Casey acquired some basic martial arts skills as an unwitting stooge of Master Khan during the year the Turtles spent in the future. However, he still prefers to go into combat with his battering equipment.