Tip: You can use Lunar Magic's Overworld Layer 3 Editing system to edit or create your own layer 3 images (castle bricks, fish, rocks) and apply unique effects per level via the Layer 3 Bypass in the main editor.
Will detect the emulator the player is using and write it to a RAM address.
It also comes with two patches:
music.asm - If you are using a certain emulator(s) it will change the music to a different song.
newlevel.asm - If you are using a certain emulator(s) and you are in a certain level it will load a new level.
http://serioushax.pastebay.net/313706 (pointless code that checks if A is 16-bit or not)
-------That one was made by tmercswims, the rest were made by me-------