It was interesting to watch - DD and I are both too strong personalities for ME to do her hair like that! It took a lot of "product" and time to get her hair into the little bun. It probably would have stayed several days, but she wanted it down that night - she was pulling out pins on the bus back to the resort. We had to wash her hair several times to get it back to "natural," but it was absolutely worth it to have that hairstyle for a day.
Edited to add more detail:
Start with a normal kid:
Swoop her hair into a pony tail and tease and tease and tease:
Add a hair piece, tease some more, and perform some magic:
Mystify some Disney friends (sorry...couldn't resist):
And amaze the subject:
Obviously, there is Disney magic at work.