Ariel from The Little Mermaid
I am thinking a purple or silver top, not necessarily a bikini top, with a green skirt. Accessories in the shape of starfish or pearls would be cool.
Jessie from Toy Story
This would be the easiest option. White shirt with these trousers which I own (sad to see they are now more than half the price I paid for them). Then a cowboy hat. Easy!
Sally from The Nightmare Before Christmas
Can you see a theme with the hair emerging?
I'm excited. I love to dress up! What is your favorite fancy dress outfit?