This could go in a lot of different directions. On the humorous side of things, Ruka could find himself in Juri's body and be totally fierce. (The boy just has an unsettling level of skill when it comes to applying mascara, what can I say.) On the angsty flipside, Shiori could unwittingly be sweet to Juri-wearing-Ruka's-body, and say all sorts of lovely things to "him", and utterly crush Juri's heart a little bit more. Touga could embarrass the heck out of Saionji by doing his normal Touga-esque things using Saionji's body; Miki and Kozue could be intensely confusing all over the place; Shiori and Juri could spend a lot of time being equal parts hot like fire and self-loathing; Utena could be adorable and blushy wearing Nanami's body and Nanami could scowl at everyone a lot before she realizes that this is her perfect opportunity to bring her excellent fashion sense into that weird tomboy's life via an obnoxious makeover. Also, you could explore the how behind the bodyswap. Could magical curry be behind it, and is Anthy just toying with everyone? Is there another reason entirely?
You could drabble about characters fencing in each other's styles; or write about a character experiencing awkward adjustment moments involving learning to move in someone else's body. Most importantly, there could be sexy exploratory bodyswap scenes involving full length mirrors and not a lot else! You get the picture.
Remember, the list of every challenge ever issued is available and up-to-date, if you're looking for a topic to write about. The challenges in this community are always continuous, so you can answer any challenge at any time regardless of when it was originally issued.
Now, go forth and write bodyswap stories!