All of the above, naturally, plus that irresistible little upward flick he sometimes puts at the end of a note, like with 'whole lot more' on Big Girl. (Hopefully someone on here who knows more about singing than me can give this a technical term!) Guess it kinda goes along with the whole issue of switching so easily between falsetto and lower register.
Not to mention, and this is a huge one for me cos I will never understand it, the fact that we love him for doing all these things rather than hate him for manipulating our poor defenceless little hearts and minds. How does that work????!