You doing, Mummy?

Matilda's favourite question at the moment is:
You doing, Mummy?
(Mummy can be replaced with Daddy, MorMor, GG ... and so on)
This means "What are you doing, Mummy?" and can be uttered at any time of day or night. Driving in to work and day care on Thursday, I was asked at least twice "You doing, Mummy?". "Driving, Matilda" was the response on both occasions.
"You doing, Mummy?" has the potential for being even more annoying when uttered at 2am. Imagine me, bleary-eyed, stumbling into M's room. M has been calling out for the urgent attention of a parent, seeking water or a cuddle ... I walk into the room, making my way towards the cot. M is somewhat awake and sitting up* - "You doing, Mummy?". Generally the response at this time is something along the lines of "Not yelling at you, Matilda".
The curiosity of toddlers ... and we're not even at Why? ... yet ...

*If M is just calling out in her sleep (much like she did from 2-3:30 am this morning), she'll still be lying down when I get there and won't stir when I enter the room. Unfortunately, it takes going in to check on her to figure this out. Perhaps a night vision webcam is called for??