Do your cats "answer back" when they get moaned at?
This is what happens in our house:
Ally does something nawtee
My hubby sez to her "NAWTEE KAT"
She opens her mouth, screws up her face and says "ACK ACK ACK ACK ACK ACK"
(Don't know how to describe the noise - sounds like the noises monkeys make when you walk past their cage at the zoo!)
She only does it to Daddeeee, not to me, and only when she gets moaned at - but it's so cute!