Let's see. I think I'll do something like this for a humorous episode. We've got:
1. Rantle, male human warrior who wants to marry Shalosha, an NPC Elf princess.
2. Fayne, female Elf warrior who hates Shalosha's father, but likes Shalosha.
3. Guthwulf, male human cleric who has a reputation as a vicious torturer. He might actually consider Rantle a friend. He's been hitting on Katrina.
4. Quill Kainen, male human wizard who's a braggard.
5. Shara, female human psychic monk who has an elder god inside her.
6. Rivereye, crystalline psion metacreationist.
7. Diogenes, male human enchanter, really frikkin' pompous.
NPCs include:
1. Shalosha, female Elf fighter-mage, princess, betrothed to Rantle.
2. Katrina, female human fire mage, sister of Rantle. Has a crush on Diogenes.
I think I'll have Shara and Rivereye, the psions, stay normal. Fayne can switch with Shalosha, making it a bit odd that she's in the body of the daughter of the one she hates. Rantle and Quill will shift, because it will force Quill to get involved in more roleplaying. Katrina and Guthwulf get to switch, because Guthwulf's player is the funniest guy in the group, so he'll have the most fun with gender-bending. And Diogenes . . . maybe he'll take turns or something. I dunno.