As incredible as it may seem, the cat-suite wasn't Catwoman's fashion thing.
Even tough it's known to had been invented somewhere in the 1940s, it wasn't until late 1959 that it became popular. Why? It had to do with science: a great thing was invented in 1959, that would chance the world of fashion (and porn industry) forever: SPANDEX!
So, the very-first the wear a cat-suit on the big screen was: Barbarella-Jane Fonda (1968)