When you change something about a game and recompile it, the exact address where the memory saves what often changes. The missingNo glitch only works because the name gets saved at the route Pokemon address, I assume that just without any reason changed to somewhere else when the game got recompiled later

This happens, because if you talk to he old man, your current name gets overwritten with the old man's name. Your original name gets saved somewhere else in the memory, at the exact same location of the memory which tells the game what Pokemon it can catch on the current route. (It's pure coincidence both get saved at the same location). Therefore, if you talk to the old man, the Pokemon you encounter is your Name's ID. However, in the city with the old man there are no locations to catch Pokemon anyway and when you enter a new route, the data gets overwritten with the new route data, therefore this does not matter. HOWEVER, if you somehow manage to trigger a Pokemon *without* resetting the data of what Pokemon you encounter, you can basically get any Pokemon you want. That explains the old man's part, but why swim up and down in that specific city? The city is bugged. You see how he is basically surfing half on land and only half on the water, right? That means he is to some extent still inside the city area and never actually entered the route. Because of that, the route Pokemon Encounter data never gets loaded into the memory and your player name ID is still in there. If you would go just a single step more into the water, the route would load and reload the encounter data. That is how it works. The game looks what Pokemon to encounter at a specific location of the memory, the old man overwrites that data with your name and glitch allowing you to surf without ever leaving the city enables you to encounter a Pokemon, without ever entering a route (which reloads the data).

@@otozinclus3593 sure but that still doesn’t explain how it even happened in the first place

@@Tarrabyte How what exact thing happened? The only thing unexplained, is how the bug regarding the half-tile still counting as city bug happened. Everything else makes sense

@@otozinclus3593 oh, I mean how people find this out. It’s so like how in the long run

@@Tarrabyte Glitch hunters try out weird stuff and try to figure out why what happens. Once you have some bugs, you can start thinking about how to use it for your advantage I think the glitch with surf is not that hard to figure out. It is not that weird that someone would surf at this specific location and the ones who did probably found it weird that the mons of the previous root appeared there. This gets easily figured out by pure accident. The other question is, how people figured out the Old Man overwrites that specific location in the memory. In today's world, you can keep track of a specific location in the memory and every time something changes there, you get notified. Glitch hunters may just play the game looking at what changes this specific location in the memory and then at some point realized the old man does. Today you would use an Emulator for this, but back in the day you had cheat devices already, maybe people just experimented with these and used these to gather data about the weird surf glitch they found?

Excuses.

yes

You can trigger the tutorial again after you got HM flying