I've been trying to hack Mega Man 2 recently, and I've managed to use Translhextion to change the weapon names and end-of-level messages (read: I had no idea what I was doing, so I opened the game in Translhextion and saw what I could find), but I can't find the copyright screen data, boss names for the boss select animations, or the Item names for the "Item-X Complete!" message. Are these stored in a format that I can find using Translhextion, or does this require a more complex method?

Thank you. With this, I've been able to modify quite a bit more. Is there a way to change the letters displayed on the weapon menu in this way, or does that require tile editing?

THE MegaMatt? I don't know. I'm the one from Legend Force EX and the hack video series on YouTube, if that's what you're asking.

Yes, I tried that, both with and without the font table I made out of SerenadeDS's post. It didn't return anything. I assumed it would be near the Get Equipped screen messages (37E22), and there is a series of letters there, but modifying it only modifies the letter at the top of the Get Equipped screen. I also tried searching for "123" so that it would ideally find the Item numbers, but nothing appeared.

Off topic: I've noticed that the hex has a lot of fragmented alphabets in it-- stuff like "fghijklmnop" and then a few bytes later "PQRSTUV".

It depends.  Start up the game and bring up the weapon menu (it helps to have all the weapons already).  Now, bring up your PPU viewer.  You should be able to see tiles spelling out "NEXTWFAQBM".  These are (some) of the tiles being used for the weapons menu. 

Now, open up the rom in a hex editor.  Through a quick (and lucky) search, I found some important data at address 35650 (that's a hex address, including the 10 byte header).  You should see 1F 9F 9B 99 9D 9C 9A 9E 10 15 16 17.

Back in your PPU viewer, you should be able to get the tile IDs by hovering over them.  In your weapons menu, your letters go P H A W and so on.  Find the 'P' tile in the PPU viewer and look at it's ID -- it's 1F.  Now get the tile ID for H -- it's 9F.  A, 9B.  W, 99.  See a pattern here?  (Look back at that hex string above if you don't).

The values at 35650 are telling the game which tiles to use in the weapons menu.  If you want it to use another tile (it can be any tile that's loaded, doesn't even have to be a letter/number), just change the corresponding hex value to the ID of the tile that you want to use. 

If you want to use letters that aren't loaded in the PPU, you're going to have to do a little tile editing.  Open up the ROM in your tile editor of choice.  Right near the top of the rom, you'll see your NEXTWFAQBM.  Just swap in whatever tiles you want there.

Thank you all very much for your help. One last question, and then I'll leave you guys alone. I've been contemplating modifying the music, and although I imagine this is most likely out of my league, I'd like to give it a shot anyway. I presume I can modify it using a hex editor of some kind, and if somebody could point me to the general offsets I should look at, I can probably figure the rest out for myself.

Thanks again for all your help.