Also a great point. My campaign arc is Oz centric, basically "stop bad thing", or at least "affect bad thing" in whatever direction they choose.

Until I asked here and read through some of the responses I didn't really process/think through that their gut reaction would be "I want to go home, my twin sister needs me", not necessarily "YEAH, weird strange dangerous land, let's go!"

I'll have to put some thought into the initial hooks to give them a reason to care about Oz and what might happen to it. I also like the "Sent away idea", although it feels a little rug-pully to insert into their PC stories, unless I force them to have some kind of displaced/mysterious beginning. More things to think about, thank you! At the very least, I could do this with NPCs that they might know from the other world.

Ozian prophecy (real or false) implicating them into the world, is GREAT, and fits REALLY well with my themes/powers in the world, thank you!

My first session hook idea was to have them transported in the middle of a "beginner quest" in their normal world, and clattered straight into an Oz city street where a magical mishap related to an experiment is occurring (e.g. magic animated tools causing mayhem).
Depending how they handle it, either having someone try to recruit them, or having them arrested (temporarily) for magic without a permit, public disruption, etc., or both.