Years and years ago when I played Gen1 I read the manual and in it was the part where they explain how legendaries (or as they where called; "rare") work and they if you fail to catch one you never get another chance.

Next to the picture was Zubat, I figured that meant that Zubats where rare and when I finally got to Mt. Moon my jaw dropped I thought a lucked out.

And than I nearly shat myself when the damn thing fainted. I panicked tothe point where I even tried catching another trainers Zubat.
Because I was dumb.