What's happening to my cactus?

[W0mbat]

So I've had this cactus for a couple of months now and still don't know what breed it is. I think it might be a moon cactus, but it's such an unusual shape and colour (at least from what Google shows me) that I can't be sure. Recently I've noticed that the top of it has started to turn green, and the little buds have also started to grow. There doesn't seem to be any evidence of rot or anything, is the top half of the cactus starting to grow on its own? I know lots of shops "graft" cacti that don't make their own chlorophyll, is this what happened with mine? Has it started to produce its own and should the top half be replanted?
Sorry if this seems like an obvious question c:

[GardeningCook]

For starters - don't worry. There's absolutely nothing wrong with your cactus. In fact, the very fact that it's starting to put out buds proves its health.

It IS a grafted cactus, but not one of the "Moon" types. What you have there is a variety of succulent (I'll peruse my books & see if I can find the name) grafted to a type of Candelabra Euphorbia, which is frequently used as base stock for cacti grafting.

Again - looks perfectly healthy to me, although you may have to keep an eye on it in case it looks like it might start getting too top-heavy. Might need some light staking in the future.

[W0mbat]

Thank you for the reply and advice c:

Nice to know the little guy's doing good, guess I'll just keep doing what I'm doing haha

[melop]

GardeningCook is correct. The top portion is a euphorbia lactea cristata variant.

[Spanishfly]

grafted to a type of Candelabra Euphorbia, which is frequently used as base stock for cacti grafting.

Actually that is not quite right. Plants can only be grafted to another plant of the same family. So a member of the family Cactaceae cannot be grafted to a member of the family Euphorbiaceae.