(Photo: Melissa Hom)

Cowboy
Most unisex vintage stores have at least one rack of rugged button-downs, making the cowboy ensemble the ultimate last-minute costume. This shirt from Physical Graffiti caught our eye for its bright color and galloping stallion motif, on top of the requisite snap buttons ($48). Cowboy hats can be more difficult to find, but Star Struck has dozens ($45) as well as generous bins of bandannas and belts for accessorizing. Of course, exhibitionists can always opt for the classic Naked Cowboy costume: Just swap the jeans and oversize belt buckle for … boots.

Girl Scout
The Girl Scout costume delivers the same cutesy punch as a Catholic-schoolgirl jumper, without having long since passed its saturation point. The tan shirtdress is a fairly common vintage find—we particularly liked the belt and red trim on this Screaming Mimi’s version ($78)—and has potential to be worn in a non-costume capacity later. The sash was fished out of a $5 bin at Love Saves the Day, and crafty DIYers can pick out their own patches from piles at Archangel Antiques for $2 to $8 apiece. Those hunting for real relics should check out the racks at Star Struck, where we found half a dozen Boy Scout and Girl Scout uniforms.