Perhaps there is a crossover where Jeff the Killer is a cursed spirit in the Naruto world. He haunts a particular forest that the ninja teams have to pass through. Naruto, with his ability to see the good in people (or in this case, cursed spirits), tries to communicate with Jeff. The rest of the ninja are skeptical but Naruto believes that if they can break the curse on Jeff, he could become an ally against the greater threats in the Naruto universe.
A plot could involve Jeff the Killer being a part of an experiment by Orochimaru. Orochimaru, always interested in unique and powerful beings, tries to combine Jeff's dark powers with some ninja techniques. Naruto and his friends then have to stop Orochimaru's new creation, which is a half - Jeff, half - ninja monstrosity. Along the way, Naruto tries to reach out to the human side of Jeff.