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.
Oh, why must I tell 'em again?
What must I tell 'em, my friend?
That we are born into sin
And we are worshiping murderers
Nothing but evil duplicitous men
I know you heard of 'em all
We should just murder 'em all
We should just murder and ball
We dance on the ruins we looting from all of they palace's walls