You like swapping genitals eh? Well in that case, I wish that your genitals would become a fully functioning female reproductive system but otherwise you'd remain unchanged.
you feel a burning in your crotch for a second and then all of a sudden it feels roomier down there. You slip a hand inside your underwear and find not the usual dick, but a rather female vagina. In shock you pull your hand out.
Heh, how's it feel? Bet I wouldn't like it, but maybe you do. Can't think why you'd put me through it if there wasn't at least part of you wishing it'd happen to you. Well then, what now? I could make that normal for your world, or make you unique. Or maybe I should bring you to my world so I can keep an eye on you. Tell you what, I'll be kind and let you choose - do you want to stay you and be normal, stay you and be a freak, or be my brother?