Having duplicates from the other world could be very interesting for Flash. I have a feeling that the Killer Frost we see first won't necessarily be the Caitlyn we're used to.
I've also got theories on Cisco's inspiration for the Flash signal being something from the other world as well.
Too deep in yearning we need
something to hold, and something to keep
Innocent eyes could not realize
the meaning of "destiny"
But someday I promise that
you’ll start to notice what’s there on your shoulders someday -
Wings that are strong,
they will guide you along to the future that holds your fate!
Let me tell you a cruel angel’s thesis -
Flying high from the window, finding egress
There is something betraying all my memories,
burning pathos, emotion overwhelming!