Also, technically, if we accept Chrono Cross into continuity (which I prefer not to), the people of Chronopolis have the capacity to create at least one artificial Chrono Trigger.
Disturbingly, the explanation of how a Time Egg is constructed, given by a random computer in frozen-time Chronopolis, is not that far from actual physics. If you *could* somehow get a black hole to spin at just the right speed to form a torus instead of a sphere, you could do really freaky things to time and space in the "hole", and that's very close to what they describe in the game.
Man, I'm just full of posting...
Disturbingly, the explanation of how a Time Egg is constructed, given by a random computer in frozen-time Chronopolis, is not that far from actual physics. If you *could* somehow get a black hole to spin at just the right speed to form a torus instead of a sphere, you could do really freaky things to time and space in the "hole", and that's very close to what they describe in the game.