This is explained by my Rifts character.
Topic: Infinite universes, finite possibilities.

Reason for this is both to explain somethings about universal travel for RPs and connecting tabletop games. That way people can still have the same character in vastly different settings with.

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*A large tan scaled scalie walks onto a balcony as the streets are full of citizens and travelers. He takes a moment to scan surroundings before addressing a audience of various races.*
"Hello, I am Marius the Grackle Tooth. For some reason I was selected from my group to explain something to you. You can grasp a infinite number of universes already in existence but the possibilities oh what is in the universes are finite. I would go into depth about what that means on a science level but I do not know how to explain that part to you. What I can explain to make this easier to understand is how people are both infinite and finite."

*He takes out some notes from his back pocket and scans through them before continuing.*
"Example, a dragon I have met in my universe has a near copy in another universe. Sure one has the powers of a demi-god while the other only has a few magic tricks, sure the age of one is in the low hundreds and the age of the other is in the high thousands. But they still look the same, act the same even though one lives in a era with almost no technology while the other messes with high technology. I have even met a version of myself that was made by scientist's test chamber while I am a naturally born from an egg."

* Marius  pauses to look over the crowd and notices most of them are either confused or nervous about this revelation.*
"I am not saying that every universe has a version of you or that every version of you has the same personality. Just that there is a larger chance that somewhere in existence their is, has been or will be another you. As for what happens if you meet the other version of you. Well the world will not explode if that is what you are thinking of. All that would happen is the event will be like... depending on their values... you are meeting a stranger or family member."

*The tan scalie taps his chin thinking to himself.*
"Well that is all I need to explain about that topic. So now some of you can show me where to find a good tavern in your universe."

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