The concept is pretty simple. Let there be a mutation that can only be obtained by claiming a rare NCL or breeding with that NCL (in which case the pass rate would be very low).

The purpose of this is not only to add some more excitement to claiming lionesses, but also finding new ways to implement mutations aside from random chance, breeding, and applicators.

As for what mutation these NCLs would have, any of the current suggestions could be combined with this idea. Curled tail could be neat, and hairless could be used as something special for the June Event (playing on Sphinx cats).

Any suggestions or tweaks in the comments are welcome.