According to this website, there have at some time been reports of Pokemon instantly becoming poisoned on exiting the Diglett's Cave. Is there any truth to these claims?
The site is both credible and not credible as a source. It claims that 'Missingno.' exists in the third generation as a roaming Pokemon with lower encounter odds than shiny Pokemon, and that wild Pokemon may occasionally either become a Celebi or have its sprite changed to that of a Celebi, but the remainder of the site's reported glitches are confirmed, apart from these:
"Poisoned From Digletts Cave
When you leave digletts acve, you could be poinsoned
This is still not proven."
"RUMOR: Poisoned Healed
Its rumored that there is a place in Viridian forest that when you walk by it any poisoned pokemon would be healed."
The possibility of this being true - however unlikely it is - fascinates me.
The reason I asked is that I once imagined it to have some practical function in Pomeg glitch research, though I can't bring myself to remember exactly what. The latter rumour does not interest me, as Antidotes and Full Heals are always at hand.