Similar But Different

Luz and Amity accidentally open a portal to a different universe, two people walk out of the portal... they walked out of the portal? The Luz and Amity that walked out looked and behaved so differently that it was hardly them. Then another set of people walked out... it was themselves... again. Just who are these new people and where did they come from? Surely they can't be that different, and surely their universe must be similar as well... right?

Or

Luz and Amity open a portal and Concept art Luz and Amity come out, then Pilot Luz and Amity also walk out and they need to find a way back to their universe.