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.
I found another problem with this. Its kind of hard to explain so bare with me. Ok, so lets say you start the game as mario. You start at Yoshi's house and then go to the right to Yoshi's island 2 and select the level. You start the level as Mario and then switch to luigi and complete the level. When you return to the overworld, you come back as Luigi, the new path animation plays, but instead of the player being on yoshi's island 2, you are back at yoshis house. Not only that but even though the path animation played, you can't move up to yoshis island 3 for some reason. Not sure why this is and id love to use this patch in my hack but this essentially breaks the game. Any way this can be fixed?
This patch is really cool. Two things. I feel like it would be better if you could only switch characters from the overworld. Other thing I noticed is if you get a game over as Luigi it doesn't end the game for some reason until you die one more time.