These kittens would be related to the ones that Alec mentioned.

When he mentions mer-kittens her eyes go wide as saucers and her jaw drops open. "REALLY!? THEY SOUND AWESOME!!! I WANT ONE!!! DID THEY TURN INTO CATS OR INTO DOLPHINS!? COULD THEY LIVE IN FRESH WATER!?" Volume control what?

Rory now hates Phoenix with all his might. Because now he's going to have to put up with Ceilidh wanting a mer-kitten and asking for one. And her finding Phoenix and seeing if he could get her one and... yes.

It shows in his expression.

Haaaate.