What is/are the spawn trigger(s) for the hidden items in FireRed/LeafGreen?

Question

This is unbelievable, but it is true. Even though the 3th generation remakes of the original Pokemon games are almost 15 years old, some tiny things are still unknown about these games, and I searched all over the internet for one of those last pieces of knowledge about the game, but I could not find it, because no one knows it.

This is about the mystery of the Mt. Moon mushrooms. It could be one of the last real mysteries of the game, bound together by other hidden item mystery spawns. I can't believe it but it's impossible to find on the internet when these Tiny Mushrooms spawn in Mt. Moon. We do know they spawn after an ingame event, just like the underground path hidden items do, and maybe other hidden items in the game. But I'm completely grasped by the fact that to this day, no one ever searched after those ingame events. They caused so much confusion (many people asked questions on all forums about missing hidden items in FireRed and LeafGreen) and no one knows.

I would like to ask all of you to help me with the final FireRed/LeafGreen mystery. We need to know exactly when those items spawn. This can't be hard if we work together on this. Or maybe this can be found in the game files? Please help. Thank you very much.

Comments

I think they reappear every day. I don't know much else.

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@sumwun they don't appear in the first place, you need to do something first. It's not about reappearing BUT there might be an ingame event as well that makes them reappear. We just don't know. It's a shame, after almost 15 years, still hidden knowledge about these games :)

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I've never known that there even ARE mushrooms in Mt. Moon... I'm going to have to find this out.

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Do you know of any other items that have a certain spawn trigger?

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The Macho Brace needed to defeat Giovanni, The sothe bell needs to complete the pokemon tower sidequest and the leftover needs to wake snorlax up. Also there is a hidden lava cookie in the right of the truck of s.s anne that needs surf

Answer 1

Hi,

it just happens that I am reverse engineering the game and found out something about this: There exists a step counter, that once it reached 1500 and the player enters a map that has hidden items available the following happens: The game randomly selects one of three hardcoded lists of items for those maps, each with different probability (10%, 30% and 60%) and reactivates all hidden items that are part of the list. It seems like the 10% lists contain the more rare items (e.g. Ether and stuff like that).
Also note that many maps only have two or one list, and if you are unlucky and the game picks a list that is not existent no items are reactivated whatsoever. I am also too lazy to write down exactly which map has which item in its lists, if anyone is interested I can share with you how one could investigate, but I am not that interested.

Comments

So the item list changes ONLY if that area is the 1500th area that the player entered?

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As far as I understood it, yes. But it is not the list that changes. The lists are fixed. If you enter one of these maps and it is at least the 1500th since the last time (or game start), the one of the three lists for this map is selected (according to the respective probabilities) and all items in this list are respawned.
Once this process is done, the counter resets to 0. I am however only suspecting that this counter is for map transitions, as I have not found the exact routine of its increase yet.

EDIT: It is not a map transition counter, but a step counter. Each 1500 steps this event is available and will be triggered. Sorry for the incomplete information.

Answer 2

The tiny mushrooms spawn after the player receives the SS ticket, and the big mushrooms spawn after the player beats the champion.
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