What's this growing on the crown of my paph?
 

Is it a keiki? Mutation? Rogue leaves? Another crown? Alien? Please see attached picture. I've only had this orchid for a few weeks...

For some reason it would only let me attach one image from my phone so here is an alternate view, it looks like its curling around the crown..

its a new fan....a new growing plant
there is a dark spot on the lower leaf of your new growth....spray it with hydrogen peroxide or if you got physan20....to rule out bacteria or fungi infestation

Interesting! I didn't realize this is how paphs grew. So will I at some point divide the fan from the mother plant?

As far as the dark spot... it looks a lot darker in the picture, it looks like it might just be mechanical damage to the plant, there seem to be a few spots on the leaves were they either bent or nicked by something but I'll get some hydrogen peroxide on it. Would it be ok to apply it with a qtip to the spot or do I need to spray the whole leaf? Should I dilute it?

You will be able to divide eventually but it would be better to wait, since the older fans, though they won't bloom again provide support for the new fans and flowers.

No, do not divide it. That is the growing habit of paphs. They grow offshoots and then the main one blooms. When the main one blooms it will never bloom again. Unless it gets to have a lot of babies in the same pot, I would not divide it

In your first picture, the "spot" on the lower part of the new fan is something you want to watch out for for the next few days.
Make sure it is not spreading.

My initial thought was some kind of rot, but it could well be mechanical damage as you said.

By the way, this is very common way of paphs making more of itself.
Sometimes new fans will come out of in between leaves or by a way of "underground" shoots that pop up at a random place in the pot.
Sometimes more than one of them, making the plant bigger faster!

You can divide large paphs, but it's best to let them grow big because plants will give you nice flower show that way.
When you do divide, make sure you have at least 4 fans per division. You can make smaller divisions and plants will grow fine, but it may take longer to rebound and skip flowering for a seaon or two.
With bigger division, you have nothing to worry about.

Happy Growing! :)