When will the first Pokemon in the party affect which wild Pokemon appear in Red/Blue?

Question

I seem to remember someone telling this to you in Pokemon blue. Some experiences of mine also seem to confirm. Anyone have more info?

Comments

It can happen with Pokemon with abilities like Static and Magnet Rise, which make Electric and Steel type Pokemon appear more often, respectfully. Many other abilities affect the chance of Pokemon spawning in general. No abilities existed in Blue however...

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Can you give us more details about the experiences that seem to confirm this? https://sha.wn.zone/p/pokemon-encounter-rate says only your Pokemon's level matters, and it matters only when you use a repel.

Answer 1

There are no held items, abilities, bike modifiers, or first-step grace periods to complicate things here.

Once the game has decided to throw something at us, it generates the wild Pokémon's level. Again, this is dead simple. Each entry in the area's encounter table has a species and a level. The species and level are randomly pulled from the weighted encounter table, then compared to the lead Pokémon's level if Repel has been applied. It doesn't check if the lead is conscious, though, unlike every other generation.

source

Comments

Nice. So I can use a fainted level 39 as lead with repel to catch raikou, and then I can challenge him with whatever pokemon I want. Good to know there aren't other factors since I was mainly concerned about not meeting the right pokemon due to my lineup.

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Raikou isn't in gen 1, though. In gens 2 to 5, repels use the first conscious Pokemon's level.

Answer 2

The first Pokémon won't change any encounters outside of hypothetical RNG and encounter manipulation glitches.

Comments

Do you have a source?

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How do you know this?

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I'm interested how "RNG manipulation glitches" in Gen 1 can allow the lead Pokemon to affect encounters. Is this documented somewhere?

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So I'm not going to source stuff when the answer is "no".

There are no abilities in gen 1, and the Ditto Special manipulation glitch can, according to some players, perma-brick a cartridge.

I'll mention it here in the comments. You can initiate a battle with an off-screen trainer by approaching them, and you can fly or teleport away from them by pausing when they appear on-screen.

If you return to that trainer, the game starts a LV 7 wild Pokémon battle that is the number of whichever Pokémon has the same dex number as the Special Stat of the last Pokémon you battled.

Make your lead Pokémon have, for example, a Special of 151 and then go fight a Ditto. It transforms into your Pokémon (making its Special 151) and then you return to that route.

The encounter will be a Mew.

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According to https://bulbapedia.bulbagarden.net/wiki/Mew_glitch , the game generates a wild Pokemon based on the index number, not the Pokedex number. Mew's index number is 21.