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Guide: 1st & 2nd GEN: Bugs/Glitches/Exploits

Which Should I Work on Next?... both will take time.

  • [B]1st Gen:[/B] Add Trainer-Fly section for which poke a trainer will allow you to exploit, w/ long-

    Votes: 2 33.3%

  • [B]2nd Gen:[/B] Call Gen 1 good & start working on Gen 2 ([U]this will take much longer[/U]).

    Votes: 4 66.7%
  • Total voters
    6
  • Poll closed .
Amy May

Amy May

Banned
214
Posts
5
Years
    • Age 39
    • Seen Nov 13, 2021
    Major 1st Gen Update

    Just finished adding all the other stuff I forgot....

    - Glitch Cloning Methods including tutorials
    .....(in "Other 1st Gen Glitches")

    - Rival (Champion) Sound/Music Glitch
    .....(in "Other 1st Gen Glitches")

    - Evolution Stone Bypass w/ all info needed including tutorial
    ......(in "Other in-battle Errors & Glitches")

    - Glitch City Glitch Exploit
    ......(direct link located in "Exploits" under "Safari Zone Glitch"

    - Plus a half dozen glitchy things in regular 1st Gen glitch walkthrough.


    Also....
    It appears 2nd Gen may end up winning the vote in a couple days!
    - if this is the case, I'll still get around to doing full 1st Gen Trainer-Fly exploit regarding exploitable pokemon through trainers (w/ long range trainer & fill in the blank tutorial).. but later down the road.
    ... I probably won't be trying to cram it in my poor 1st Gen post either. xD
     
    Last edited:
    Amy May

    Amy May

    Banned
    214
    Posts
    5
    Years
    • Age 39
    • Seen Nov 13, 2021
    Sorry it looks like I threw up my 2nd Gen post!!!

    There's still much to add/work on/sort out. I figured it would be best to just post what I have at this time, rather than hold off on it a few more weeks.
     
    Last edited:
    Lucifer

    Lucifer

    Fallen1
    362
    Posts
    13
    Years
    • I just learned about an R/B glitch that soft locks the game that I thought might be a good add to this wonderful guide.

    Apparently, without a Pokedex, the game isn't programmed to be able to process any pokemon on the file except a first form starter so if you evolve your starter before delivering Oak's parcel Oak will rate a phantom Pokedex instead of accepting the parcel. Without the completion of the parcel event which results in official recognition of a Pokedex, the Old Man will never get his coffee and let you pass thus you'll never be able to leave Viridian City!

    I'm guessing this is what happened to Ash's dad, Delia said he never got passed Viridian City. ;D
     
    Last edited:

    aminmasaleh2

    Banned
    1
    Posts
    4
    Years
    • Seen Jun 9, 2019
    Oh sorry about that, i did read quite a lot
    Its just, theres quite a lot more to read you know

    You gotta admit though, the game breaking ones are the most interesting arent they :P

    Thats what i usually do these days too, i mostly do them to get to places quicker
    Man these game are broken if you know about the cracks in the code
     
    Storm Knight

    Storm Knight

    That one guy who's always standing around Kalos Ro
    2
    Posts
    4
    Years
    • Hey, so, uh, I was hoping I could get some help here. I understand there is a way to get LV 100 Pokémon before fighting Brock, but I was wondering if there was a way to get a LV 100 Blastoise.
     
    itsdarsh

    itsdarsh

    Contender
    20
    Posts
    4
    Years
    • Ecruteak City Save Bug

    The cause of this issue remains unknown. It affects saving/rebooting in all of Ecruteak City. In the entire span of mainstream Pokemon games, Ecruteak City is officially the only location ever categorized as a "Glitched City" due to GF rendering it as unfixable. The Ecruteak City Save Bug is present in *All* games (both mainsteam & fan games) involving Johto mapping containing that location.. including HGSS. This is due to the Johto base mapping coming from 2nd Gen, which also comes with the majority of it's original glitches.
    - Unless some Einstein ROM hacker figured this one out, the direct cause of the save bug is still unknown.
    Click to expand...

    Does anyone have any further information on this? I'd love to investigate it but I cannot find any information on this on bulbapedia, GCL, serebii, pret, or anywhere else really. A source would be much appreciated.
     
    Raicheot

    Raicheot

    398
    Posts
    4
    Years
    • The annoying thing about the mew clitch is you can't move the pokemon to bank, I wasn't able to move my Lapras that I got with the glitch, prob would of worked if I move to a gen 4 game and put through or cloned via pksm
     
    Momoro

    Momoro

    I'm gonna put some dirt in your eye..
    269
    Posts
    4
    Years
    • Liquid Halo said:
    I just learned about an R/B glitch that soft locks the game that I thought might be a good add to this wonderful guide.

    Apparently, without a Pokedex, the game isn't programmed to be able to process any pokemon on the file except a first form starter so if you evolve your starter before delivering Oak's parcel Oak will rate a phantom Pokedex instead of accepting the parcel. Without the completion of the parcel event which results in official recognition of a Pokedex, the Old Man will never get his coffee and let you pass thus you'll never be able to leave Viridian City!

    I'm guessing this is what happened to Ash's dad, Delia said he never got passed Viridian City. ;D
    Click to expand...

    Haha! YES!
     
    Megan

    Megan

    23,297
    Posts
    11
    Years
    • She/Her, It/Its
    • Seen today
    I just recently saw a video in which someone ran into a glitch that I've not seen any coverage, yet, period. That's probably due to how situational it is. It involves The moves Transform and Disable. If one of your moves is disabled and your Pokemon uses Transform against your opponent, and the opponent also knows the same move but in a different move slot then it will still be disabled. But the UI won't show until you click it. However, the move that replaces the old disabled move will also be disabled.

    I suppose it's better to link the video (also to give credit): Video
    Just go to 5:30.
     
    jojobear13

    jojobear13

    536
    Posts
    4
    Years
    • Seen yesterday
    Megan said:
    I just recently saw a video in which someone ran into a glitch that I've not seen any coverage, yet, period. That's probably due to how situational it is. It involves The moves Transform and Disable. If one of your moves is disabled and your Pokemon uses Transform against your opponent, and the opponent also knows the same move but in a different move slot then it will still be disabled. But the UI won't show until you click it. However, the move that replaces the old disabled move will also be disabled.

    I suppose it's better to link the video (also to give credit): Video
    Just go to 5:30.
    Click to expand...

    Found the cause. Here's what's going on. The battle engine assumes that only Ditto can use transform, and Ditto cannot have any other moves under regular circumstances. But this bug can happen because of the extremely late addition that was Mew. Per bulbapedia:

    In an interview with Game Freak and Creatures, Inc. in Nintendo Power issue 134, Shigeki Morimoto revealed that he created Mew two weeks before game development was finished.
    Click to expand...

    With only two weeks before the deadline, there was no time to adjust the battle engine to account for the fact that Mew can learn transform as well as other moves.

    The transform effect needs to do the following to fix this:

    if enemy transforming
    ld [wEnemyDisabledMove], 00
    ld [wEnemyDisabledMoveNumber], 00
    Click to expand...
    if player transforming
    ld [wPlayerDisabledMove], 00
    ld [wPlayerDisabledMoveNumber], 00
    Click to expand...
     
    jojobear13

    jojobear13

    536
    Posts
    4
    Years
    • Seen yesterday
    Here is one for Red and Blue.

    In saffron city, when the silph co dungeon becomes available, there is a rocket guard outside the building who has fallen asleep at his post. This NPC has random facings, but he is actually supposed to face downward.

    This is because he is the 15th object in the saffron city map header. The true bug is that 15th object for any map will have incorrect facing. There is a reason for this.

    In the function that updates npc objects, the facing value for the 15th object is stored in a temp location at $D500 (previous object facings occupy preceding addresses). The function loads a base address of $D4E4 into the HL register, and then it points it to the correct address by summing L with a calculated offset in the A register. The problem is that the value in H is not incremented if the sum exceeds $FF, so the facing value for the 15th object is incorrectly loaded from $D400 instead.

    Side note: The issue is moot in Yellow version. This NPC was removed in Yellow, and Yellow cannot have more that 14 objects in each map's header. This is because the following-pikachu occupies an object slot.
     
    RatataBiker

    RatataBiker

    103
    Posts
    2
    Years
    • Seen Oct 19, 2021
    Ah the Missingno glitch, I used it many times. I even captured him. I also remember that I had a bugged Electrode level 250
     
    jojobear13

    jojobear13

    536
    Posts
    4
    Years
    • Seen yesterday
    So the missingno issue in gen 1 is quite well-documented. But I wanted to zero-in on one aspect that gets missed a lot. That being how random encounters are determined based on where you are standing.

    Each walkable space is made up of four individual tiles: upper left, upper right, lower left, and lower right. Whether or not you can encounter something as well as what list to use depends on the tile you are standing on. But how does the game know which one if every space has four tiles? Well, the game simply references the bottom two tiles of your space. The lower right tile determines if a land or water encounter can occur, and the lower left tile determines the encounterable list.

    Uh oh. Can you see the immediate problem? This works if both bottom tiles are grass or both water or both cave, or both no-encounter tiles. But what if they get mixed and matched? This is what happens with eastern shore spaces like the cinnabar shore. Water as the lower right tile and town ground as the lower left tile. A water encounter gets generated with an invalid list of bogus data. This is easily fixed by making the encounter check and encounter list reference the same tile coordinate instead of two adjacent ones.

    This is also ties into the cause of so many grass spaces in the viridian forest and safari zone that will never give encounters. Check the lower right tile of such a space. It will have kind of a 'star' shape that's different from the typical two-blade grass tile. That 'star' grass tile does not actually count as "encounter grass", so having it be the lower right tile nullifies encounters for the whole space.
     
    jojobear13

    jojobear13

    536
    Posts
    4
    Years
    • Seen yesterday
    New bug for Gen 1 games. This time it has to do with menu inputs.

    When on a menu, pressing A or B simultaneously with UP or DOWN will register both inputs with UP/DOWN being handled first followed by A/B. This can have some odd effects.

    Here's an example. Place the cursor over AREA in the pokedex menu for any pokemon entry. Then press DOWN+A. You will exit from the pokedex instead of going to the area map. Why? Because DOWN is handled first which tells the game that QUIT is being selected. Then A is handled second to confirm the selection.

    The solution to this weirdness would have been to have A/B handled first and have them take priority over UP/DOWN.
     
    jojobear13

    jojobear13

    536
    Posts
    4
    Years
    • Seen yesterday
    This one isn't so much a "bug" as it is a bad coding practice. It has to do with Twineedle's effect in the Gen 1 games.

    Moves that hit multiple times (twineedle, fury attack, etc) are handled in their own function called TwoToFiveAttacksEffect. In this function, the number of attacks are loaded into the A register in order to later be saved in WRAM.

    Twineedle is special in that it has the poison side-effect that gets applied after its regular effect. This function checks for twineedle, and if found it loads the value for POISON_SIDE_EFFECT1 into the location pointed to by the HL register so that the side effect gets carried out after the attack. Then it sends the contents of the A register to be saved in WRAM. The problem is that the A register at this point holds the value for POISON_SIDE_EFFECT1, and the only reason you get the correct number of attacks is because this value just so happens to equal 2. If the value for POISON_SIDE_EFFECT1 gets changed to anything else, then that is going to be the number of attacks assigned to twineedle.

    Fun surprise if you're working on a gen 1 rom hack.
     
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