This is the inverse of the philosophical conundrum known as The Ship of Theseus. The Athenians preserved the original ship of the hero Theseus for hundreds of years. As one board rotted or was infested with vermin, etc, it would be replaced with new wood. Eventually there was no original wood left on the ship. Is it still the same ship? If not, at what point did it cease to be the Ship of Theseus?
Another conumdrum, which combines the original Ship of Theseus with the inverse is "Which is the real Nick Chopper?" In the later Oz books, we learn that the Tin Woodsman was originally a real human being named Nick Chopper, who was cursed by one of the wicked witches. (I don't remember which one, but that's not important.) Under the curse, a missed swing of his axe took off an arm, and he had a tinsmith build him an artificial one. But the curse was not finished, and one by one he lost and replaced aAnd ll of his body parts until he was entirely made of tin.
In the meantime, the witch had made a golem or robot for herself, and every time Nick lost a body part, he would get it and would use it to replace the corresponding body part on her creation. So once the woodsman was all tin, the robot was all flesh -- Nick's flesh. So which was the "real" Nick Chopper?
Each of these versions of the conundrum has several proposed solutions, but there is no