The bride always tells the bridesmaid that she can wear her dress again. All you need to do is shorten it, right? The same goes for your prom gown. Maybe you think you'll find another use for it, but that opportunity just never comes around. That's why you have a unique advantage on Halloween if you decide that a fancy dress is exactly what you want for your costume. Pull the gown out. And just in case you've donated that old thing to charity, duck into the nearest thrift shop and buy another one. Once you have the dress, adapting it into a fun and unique costume is easy. Grab a pair of scissors, some inexpensive make-up and props and get ready for Halloween.
Princess or Fairy
Choose to be a princess, based on the colour and style of your fancy dress. Light-coloured dresses can be dyed, but that is an extra step you can avoid if you choose to be the right princess. Dress as Cinderella if you have a light blue gown, or be Sleeping Beauty in pink. A few snips at the hem will make a long gown a short one, so you can go as Tinkerbell or another fairy by simply adding a pair of store-bought or homemade wings.
Score a cheap wedding dress at a second-hand shop, and alter it. Dresses that are old fashioned or out of style actually work better for the zombie look, so just find a cheap fancy dress that fits. Age the dress by dragging it through dirt and strategically ripping it with scissors. If you want to be scary, accent with stage blood or red paint; otherwise go for a "just climbed out of the grave" look.
Hem a long bridesmaid or prom dress as short as you dare. You don't need to be able to sew. You can use inexpensive fusible hemming tape instead of a needle and thread. Add a pair of fishnets, a choker and a headband; pair with sparkly jewellery and high heels for a fun burlesque look. Brush up on your dance steps and get ready to be the centre of attention if you go for this daring look.