My sister's little girl, Charlotte, is 27 months old and quite a clever little lady.
My sister and BIL have been using the 'naughty corner' (as per supernanny's suggestion on every show) for a while but my darling niece has rendered it useless.
If Charlotte is asked to do something and does not want to she knows that the eventually outcome will be that she has to spend time in the naughty corner so she skips the middle bit and puts herself in the naughty corner straight away so it cannot be used as a punishment for not doing as she is told.
Got to love her