Held Item Duplication in Dragon Warrior Monsters 2 (GBC)
Surprise, I'm a glitch hunter now!
Well, "bug noticer" is a bit more accurate. I stumbled upon duplicated held items during my routing for Max Catalog, and eventually deduced where they were coming from. Even if my technical explanation doesn't end up being 100% accurate, it at least paints a useful picture of what's happening in the code.
This trick is handy, but definitely doesn't break the game. You can get maybe ten or so duplicated held items per save file total - the limiting factor is NPC breeds, which are a scarce, difficult to utilize, and non-renewable resource. As such, I won't be considering it a "glitch" disallowed from Glitchless Max Catalog (No Link Cable), my big years-long project of a run. All this bug does is give you a few more held items that if you want you can sell for money, but otherwise just make you a little more effective in battle. You don't get any direct progress on beating the game or clearing out your catalog, and there's a noticeable time investment required to utilize and profit from this technique. Also, you can activate this bug entirely by accident, as I did at least three times before finally deciding to stop what I was doing and investigate. Calling it a "glitch" feels too harsh, to me. It's a bug. Unintended, but more of a programming oversight than a true exploit of the game's processes.
If opinion on this is super strong I might refrain from using this bug in the speedrun anyway, but even if that happens, it's OK. My route does not require held item duplication in order to function. Probably just a little time loss. We'll live.