Sprite RAM Bug
There is a flaw in the GameBoy hardware that causes trash to be written to OAM RAM if the following commands are used while their 16-bit content is in the range of $FE00 to $FEFF:
inc rr dec rr ;rr = bc,de, or hl ldi a,(hl) ldd a,(hl) ldi (hl),a ldd (hl),a
Only sprites 1 & 2 ($FE00 & $FE04) are not affected by these instructions.
Game Boy Color and Advance are not affected by this bug.