Dawn dresses to impress Xander that fateful Halloween night. Tagging along with her sister to the costume shop, Dawn is quickly forgotten for (in Dawn's opinion) a monstrosity of epic poofy proportions. Browsing the aisles by herself she finds the perfect costume.
In the mind of young Dawn, Xander must only like Buffy because she's strong, a hero, right? So what better costume to finally catch his attention than a powerful girl from the future?
Sadly, the costume information card said nothing about the state of River Tam's mind or the horrors she has witnessed.
I'm a Rayne fan, big time, so if you want to make this a pairing later on or make Dawn older I'd love it if the male part of the equation dressed as Jayne. It would be even juicier if Xander's so called 'soldier' was really a mercenary from the future called Jayne. :) He just needed a gun, right? Vera, anyone?