Most ROMs are labeled with "(Europe)" or "(USA)", meaning PAL or NTSC. However, some are labeled "(World)". At first, I didn't think twice about this, just assuming that that the game was released world-wide identically, with no changes between the regions.
But then I thought: "Wait a minute. This makes no sense. How can it be a single copy for both PAL and NTSC?"
Does a "(World)" NES cartridge really have both PAL and NTSC copies of the game on it, and somehow is able to automatically detect whether it's being played on a PAL (European) or NTSC (USAian) NES? I suppose that is reasonable, if the NES has such a "flag" that the game can check upon boot, but does it really have such a thing? Does "(World)" really mean this?
I can't remember any NES game which had a menu where you had to pick your region at start.