For those of you who want to be whimsical without wearing a costume at all, look to Amélie from Amélie. This one is basically a “what you already own” costume with a cute twist. The uniform is a simple dark t-shirt, a green jacket (or cardigan), and a red skirt or scarf.
Short, dark hair with blunt bangs is the goal, but a simple black wig or some hair gel works wonders. You’ll spend the whole night looking like you’re about to do something mischievous and adorable. It’s the perfect low-effort, high-charm option.