Many of these glitch maps in Pokémon Red, Blue, and Yellow permeate the unused entries in the list of locations by index number in Generation I and in Generation II.
Although the glitch map cannot be explored, it may still be possible to load data from that map, such as its Town Map or Pokégear map name.
Additionally certain glitch maps, 'semi-freeze maps' may only freeze the game under certain conditions, as is the case with Map 0xFE (English Yellow) and Map 0xFE (Japanese Yellow) which requires the data at 0xDC0E in WRAM to be safe.