This is the sound that Gwen makes when she is sort of asking permission to do something she knows she shouldn't. Sometimes she will do it anyway, but mostly if she is acknowledged properly, and she knows my full attention is on her, it is simply enough to shake my head no and then nod with a smile when she chooses to do something else.
It's not always so easy and sometimes we have to talk about not doing things because of blah and blah. I Never say a simple "No," I've always felt she deserves an explanation, even if it is as simple as "No, you can't have those goggles, they belong to that little girl and she might get sad." Strangely for the most part this works.
There are a very few occasions where it doesn't and that's my prompt to check the time. We might be overdue for our morning /afternoon tea or nearing nap time. Otherwise it's time for mummy to get creative with a distraction and make doing something else amazingly much more fun than the thing she was about to do.
I've never labeled her naughty, but she knows what the word means. A few weeks ago we almost ran over several "naughty chickens who where crossing the road without holding anyone's hand." So if she is being exceptional cheeky I sometimes ask her if she is trying to be a naughty chicken.
This gets either a giggle and she does something else or a very serious expression and a talk about how you have to "hold hands, naughty chicken cross road." If our chickens have recently broken into the veg patch then she labeled them naughty as well, but most often she adds to our conversation about road crossing that her chickens are good chickens.
I adore that at not quite 2 years old she seems to recognize such big concepts, especially that she can't see herself fitting that label, except very occasionally in play.