Good catch. I patched it for the next release. Picking a duo-outfit will now remove both players from the selectable players list. There is still a way to make this happen by picking both players first then changing their outfits, but it can't happen by accident anymore, so that's good enough for me.
Here's your reward. A sneak preview of Candy's new outfit, created with the new EZ-render setup. The background is actually pre-rendered, so it doesn't require owning any of the room assets, and it's much faster to set up and render. There's only one angle and it's limited to standing poses, though, but doing renders in that room is hard and slow, so anything that speeds it up is a win.