Do you ever have one of those moments when it suddenly occurs to you how odd something is? You know, you've sort of been living with the odd thing because it's just how things are – but then one day, you sit up and think 'hang on a minute...!'
It happens all the time round here, but the thing I am talking about specifically is Ava and Ruby's tendency to turn into cats.
For ages now, they have loved playing a game where they're both cats. One will be the Mummy cat, the other will be the Baby cat, and they might assume those roles for an hour at a time.
When they are fully engrossed, they talk only in cat (even to me).
Mummy cat tells baby cat off: "MIAOW. Mia-miao-mia-MIAOW!"
Baby cat says she's sorry: "Mew-mew."
Mummy cat and Baby cat make friends again: "Prr, prrr, prr, prrr. Miaoooow."
But cat language is not only confined to this particular game. They'll both temporarily turn into cats whenever they feel that being a cat might somehow improve their chances of coming out on top in a situation.
For example, Ava has finished her ice lolly, and wants to see if Ruby will now share hers. She drops to all fours and becomes Baby Cat: "Mia-oooooooow?"
Ruby, assuming role of Mummy cat, instantly offers Ava ONE lick of her ice lolly. Because that's JUST what Mummy cats do.
Or, perhaps Ruby has snatched something from Ava and is refusing to give it back. Ava opens her mouth to yell for me, in the hope I shall restore order... at which point, Ruby drops to all fours and becomes Baby Cat: "Mew-mew." ("Sorry.")
Baby cat gives the thing back. Ava becomes Mummy cat for a minute and forgives Ruby's behaviour, in a cat-like way. And then they start talking normally again.
It's all very well being cats at home (and believe me, I don't care what flippin' language they're talking as long as they are managing to sort out their own arguments about tiny little buttons and wotnot). But it's when they turn into cats outside the house...
We were at a playground – a packed playground, full of small children and watchful mums and dads. I realised several eyes were on Ava and Ru as they played, fully engrossed, as cats.
It went on for ages. The onlookers were initially a little enchanted (I told myself) with their game – especially what with all the rubbing noses, and the using paws to clean each others faces, and the soft little miaows to greet each other.
But suddenly, things turned a bit ugly. Baby cat had run off with the stick. Mummy cat had wanted the stick to clean the house with but Baby Cat simply wasn't playing ball, no matter how much she was MIAOWED at.
Now, I understood that this was all part of the game. I understood, because this kind of game is played on a daily basis indoors. They weren't really arguing – they were just playing a game of arguing cats. The issue of the stick was seemingly a very difficult thing to resolve.
They started hissing, and baring their 'claws' at each other. They were arching their backs and yowling and growling – and because they had also been outdoors for more than half an hour, they looked more than a little bit feral if I'm honest.
From a short distance, I glanced at the watchful parents around me. Two small children, twins I think, probably aged about two and a half, had stopped playing in the sand pit, and were staring at Ava's and Ruby's antics, stock still, wide eyed and open mouthed. Their mother sidled over and gently prised them away.
And that's when it was I realised how odd it is, their game they love so much. It was at the very moment I thought to myself: 'I wonder if that woman thinks these two children have been raised by wild cats. Nah, we're in East London – she's probably thinking foxes..."
I enjoyed the oddness for a moment, then went to tempt my girls home. "Girls, shall we go get you some fish for dinner?"
They stopped hissing. They purred instead, and rubbed their grubby faces on my knees. I gave my best 'what can you do?' face to the watchful parents, tickled my cats' chins and, tails aloft, we started to make our way home.
More on Parentdish: Let's pretend. The rules of role play for parents