Improvising moves and...switching parts...!?

There are a couple of times during the show when the gorgeous ladies switch things up on stage. They pull out new moves, they swap who's in the ring, or they mix things up on the fly, like they're improvising with Colin Mochrie.

The biggest two, for me, came in season three, when they slap together a full Christmas Carol adaptation in a very short amount of time (unless I've forgotten the time frame in that episode) and then when they decide to swap parts.

Is this common in wrestling? Anybody out there with backstage knowledge of wrestling could help set me straight, but it doesn't seem tenable.

They'd have to learn lines, blocking, and most importantly (and potentially dangerously) fight choreography.

Weirdly, the whole first season is about them struggling to create and master these moves safely, and put the show together through trial-and-error.

I love the show - I think it's great. But it seems like the writers are completely ignorant as to the nature of live shows and their relationship to rehearsal and fight choreography. But I'm not familiar with wrestling. If there is a mechanism in wrestling entertainment that allows for this kind of improvising...well, I stand corrected.