Glitch mail
Glitch mail is mail inside your inbox on your PC in Pokémon G/S/C that has glitch text and may cause a Glitch Dimension to occur. Later glitch mail near the number 25 have a tendancy to do this. It is usually received from battling a glitch trainer in the Viridian Trainer House. This trainer is usually made by turning off the power while the game is saving, doing glitched link activities, or corrupting Mystery Gift by having ifrared interference during the "gift exchange."