Can you feel the love tonight?
Because the top part of the graft, Gymnocalycium mihanovichii can't produce chlorophyll on it's own, to survive, it's grafted to (usually) a short-lived tropical Hylocereus spp. Therefore, the whole thing usually doesn't live more than three years. However, the top can be grafted to a different bottom if one knows how to do such things. I learned that the first mutant seedlings were discovered in the 1940's and that now 98% of these come from Korea where they're produced by the millions.
If one gets the urge to try doing this, here's a helpful video to show you how.
Try not to judge me too harshly. It's nice to feel loved! Now go hug a cactus.