Here's a weird idea- When real fashion from a specific time period becomes "a costume" when it's used in a performance?

Then a designer decides 

to use a sleeve or a silhouette for part of their collection and suddenly its fashion all over again. 


Pippa has much more in store for you so please check back. 
Look at silhouette (shape) of  each dress.
Can you describe the 
fabric?  (heavy, light, decorated, plain, expensive,
everyday, )
do you see any similarities?