"Dragon Quest III - Soshite Densetsu e... (Japan)" GBC has a serious bug that we can go debug mode.
When we use a bugged item called "なし"(nothing), junk data is written in RAM, and it usually freezes, but we can sometimes go debug mode.
On real console, the graphics are not broken, though the graphics of the fields are broken on Gambatte.
cheat code to put the "なし" item in the item box of the first man .: 01E58AC5
in debug mode, we can go ending credit, when we choose "4. MORIテスト"(MORI Test).
We can warp anywhere you want, when we choose "2. ひぐち テスト"(Higuchi Test).
in both case, the graphics of the field are corrupted.
many emulators seem to have the same problem.
Only on bgb, the graphics are not broken. i think it may help the analysis.
replay movie file(no cheat) : http://www.mediafire.com/?63gn1g4p1w5f2c7 (works on Bizhawk that use Gambatte core)
mp4 of the replay movie: http://www.youtube.com/watch?v=-BPMbCj2J38&feature=player_detailpage#t=385s
VBA-M makes the same broken graphics too. :
movie file for VBA-M: http://tasvideos.org/userfiles/info/2162614622808571
The graphics are not broken on real GBC console:
http://www.youtube.com/watch?feature=player_detailpage&v=oyjXuMf9nyI#t=594s (he uses GBASP?, i used to enjoy the bug on GBC and remember no graphics broken too)