Oh yeah, and it wasnt just zubat.
Really, you just need to find a pokemon that has your weakness, but that attack doesn't do damage. Like a lot of pokemon could learn thunder wave, but didnt always learn another electric attack. So if you used a bird pokemon or a water pokemon, they would just spam thunder wave. Of course, you would get paralysis, but you wouldn't die. However, you can't count on this glitch. Int he first gen, they did have a few cases where the pokemon would eventually pick a different move. I think when the games were translated in to blue version (because in Japan, they were originally Red and Green), they added in a failsafe for when an attack was used often, but the other pokemon wouldnt take damage. I know they certainly did that with Generation 2 (which, btw, had the biggest AI leap out of any game in the series)(AI code quadrupled going from Red/Blue to Gold/Silver).
EDIT: Yes, I am full of useless random facts. Lol.