Don't ask me why I tried this, but I was attempting to play a Wisdom Tree Game Boy game (Exodus, if you must know...) on my GBA and the cart didn't fit into the cartridge slot. I figured it was incompatable since it was a different cart design, so I plugged it into the GBC GameShark and tried it that way. It refused to work. At that point I was worried the cart was damaged, so I dusted off my old grey clunker and tried it in there. Worked on the first shot. It worked on the first attempt. So it got me thinking...Other than the other Wisdom Tree games, are there any games that are incompatable with the GBA, or is it just those ones?