Feeding the cat and disposing of the subsequent toxic waste.
Interestingly she's produced some of the most benign (and in tiny quantities) cast waste I've ever had to deal with. Even in non-clumping litter, it's very dry, and almost odourless.
I can hear her thudding about next door, I don't know what she's doing, but she's clearly having fun doing it! I'll go a deal with Kai first, since (i) I need to go to the loo, and that involves the bathroom, so I can't avoid waking him up & (ii) I won't disturb her, and stop her doing whatever she's doing to the Shoelaces of Doom/Squeaky Mouse/Random rolling toy.