Jimmy creates a fountain of youth and immortality. Then Jimmy tells one of the humans about it. That human probably goes mad and dies, but not until he tells other humans. These humans try and seek out the fountain. When they drink from it, Jimmy gets to play with them forever. They'll go mad, but they will never die.
EDIT: Make sure to dispose of insane immortals in a black hole when you are done with them. Leaving them on the planet can spoil the whole thing.