Bugs:Super Game Boy 1 and 2
This page details bugs of Super Game Boy 1 and 2.
There are a few graphical oddities and neither were addressed or fixed for the Super Game Boy 2 release.
When palette settings are enabled, press either light or darkness setting on either four palette settings then immediately press L + R to exit the menu. You will now see the frame of the icon for a few seconds with the incorrect palette.
Palette Row Sprites
Enter the palette setting menu and wait for the custom border to load and you will see that the last two rows are actually sprites.
Enabling PAR code 80C006E2 7EC200E9 and going to the soil border allows you to replace any icon with this unused star. This specific star uses a different texture than the other stars.
These glitches of sorts will show unused border tiles and unused palette attribute settings; examples provided.
Menu Border Glitch
Normally when a custom border is loaded into the SNES's VRAM, only the first border will switch over from the default Game Boy border to the custom border automatically. When you are in the custom graffiti menu and the custom border is loaded into VRAM, you will be pulled out of the menu and the custom border will be switched only when you are on the default Game Boy border.
However, since multiple borders can be loaded replacing the previous one, an oversight on Nintendo's part will cause additional borders to pull you out of the menu and load the custom border only when you are on the default Game Boy border, while this should only affect the custom border.
Custom Border Glitching
Custom Super Game Boy borders are loaded into three parts since you can only send a maximum of 4KBytes of data via VRAM at a time; two chucks of CHR_TRN is split up into CHR_TRN 99 00 and CHR_TRN 99 01. PCT_TRN A1 00 includes border palette and CHR placement information data and is transferred via PCT_TRN. Loading a new border will overwrite the currently loaded border resulting in glitched pieces comprising of both the old and new border mixed and can be seen when setting the border to the currently-in transition border from any other or while exiting a custom palette or graffiti menu. Nintendo, however recognized this issue and the Super Game Boy will reload the new border again.
Custom Palette Glitching 1
A glitch exists where setting the PAL_TRN 59 command without setting palette data will display this palette as the scheme for 1-A. Since this cannot be seen normally, an example of seeing the glitch would be to use the "Start in Debug Menu cheat" from Rock'n! Monster!! while enabling palettes with the additional Game Boy Game Genie code 004-10C-E6E. Changing the palette will remedy the glitch.
Custom Palette Glitching 2
Clicking on the Camera icon when playing games that allow palette settings will cause the current palette settings to alter with the new palette settings until the game area is unfrozen. Exiting the menu with L + R will leave the settings until the palette changes again.
Finding unused palettes is possible by exploiting this glitch, as seen in this example from Game & Watch Gallery 3, where exploiting the palette glitch from a black-and-white game will show that the controller buttons were simply attraction masked from the original Japanese/European SNES multicolored controller buttons to the purple-and-blue US set instead of actually assigning an updated palette setting.