as a feather
The light dressed up for the costume party as a feather.
The light dressed up as a feather for the party.
The light dressed up for the costume party as a feather.
The light dressed up as a feather for the party.
The light dressed up for the costume party as a feather.
You can find the party dress in the shake it up studio
formal
A 'fancy dress party' is not generally a 'costume' party, but an event where you would wear formal clothing such as an evening gown or a tuxedo.
I think you should come to FashionTIY. There are lots of clothes for the party.
To a fancy dress party? yes.
As_a_feather
I would dress up as grapes. A bit dumb but still.