u/Aeredren

Yayyy ! Did you know you could get grimer way before Cinnabar Island, as soon as you got the super rod on route 12 ? This can be done with only 2 badges if you skip gym 3 and 4 and only focus on kicking team rocket ass.

It only spawn in cinnabar's pokemon lab AND the pool in Celadon city, where he has 1% chance of being fish with super rod. The only other Pokemon in this fishing pool are magikarp so there is no way anybody found this by him/her.self lol !
You can also get a 1% chance koffing by surfing there.

I caught it cause I am doing a soft "prof oak challenge" I called "Prof birch challenge" :)