Obscure References in Pokemon

Remember the trivia section on Bulbapedia? There are quite a few references that are not included because few viewers know about them. Let's start filling some of those in. The reference must not be obscure because it is not in the translations like with "Do Coil Dream of Electric Mice!?" from the original anime
Here's the start of the list: Grimer is an allusion to the Four Big Pollution Diseases of Japan. This is most obvious for the Hoenn Region, where Grimer's origins match up with how Minamata disease started.

Minamata disease was caused by sludge getting hit with moonlight radiation?

I meant that Grimer's origin is at least partially a reference to it in that it is at least clear that Grimer seems to be like mercury in some respects and the Pokedex states that it it came from a bay within the Hoenn region, which maps to the Japanese island of Kyushu. Minamata disease was first documented there and was caused by mercury being dumped into the bay.