In the first film, he is portrayed by Elias Koteas. Jones was first introduced to the Turtles in an altercation with Raphael. The two of them actually fought each other in a New York City park, just after Raphael stopped some punk from stealing a woman's purse and Casey was about to beat them to a pulp for that whereupon Casey turns his aggression on Raphael. In the initial altercation, Jones used two Jose Canseco bats, which Raphael sarcastically asked if Jones in fact paid money for them, and a cricket bat to put Raphael in a garbage can.
Casey later sees Raphael alone on a rooftop surrounded by Foot soldiers. Jones proved to be very useful in a fight when he joined the Turtles while they were being attacked by the Foot Clan above April O'Neil's store. He is referred to by Michelangelo as "Wayne Gretzky on steroids". Casey Jones joins the Turtles to assist them against the Shredder and the Foot, and ultimately rescues Splinter from the Foot Headquarters. He also deliberately set the garbage truck to compact the Shredder, simply stating "Oops".
After a rocky start, Jones developed a love interest with April O'Neil, and the two of them kiss at the end of the first movie. Casey Jones origins are not revealed, but he did tell April that he played hockey professionally before he got hurt less than a year afterwards.
Despite his significant role in the first movie, as well as his developing relationship with April O'Neil, Casey is absent for the entirety of the second film. Oddly enough, he isn't even mentioned.
In the third film Casey is once again portrayed by Elias Koteas. When the Turtles made their decision to travel to feudal Japan to rescue April O'Neil, Michelangelo recruited Casey to help Splinter keep an eye on Kenshin and the Honor Guards back home at were transported to the present when the Turtles would take their place in feudal Japan. Although very much subdued from the original film, Casey was still very much himself, and helped teach the finer points of living in the 20th century to the visitors from the past. Koteas also performs an ancestor of Jones named Whit, who like his descendant ends up helping the Turtles despite anti-heroic tendencies and he also shows a romantic interest in April, just like how Casey does.
It is implied that he had moved away for a time and has finally returned to New York.
Casey appears in the 2007 TMNT film, and is voiced by Chris Evans. Casey is now living with April, and it is shown that he has commitment issues because April is ready to get married but he isn't. He works for April's shipping company as a delivery man, spending his nights continuing his vigilante activities. Through this, he meets Raphael as the Nightwatcher, becoming his sidekick - though he claims Raphael is the sidekick.
At the beginning of the film, he is the only character to know that Raph is the Nightwatcher when he meets Raph in costume, the latter is at first confused; Casey states, "Wasn't that hard, man. Y'know, you look like a big metal turtle," and Raph says, rather despondently, "It's that obvious, huh?" He's still pretty much the same person, but not as rough as he used to be. He assists the Turtles on rescuing Leo and saving the city from Max Winters' evil generals. Casey loses his plastic hockey mask, but near the end of the movie (before they go to Winters' Corp.) April gives him a stainless steel hockey mask that looks exactly like his old plastic ones.