I personally always liked the fan Pokémon concept of basing a poison/ice type after a cold, with a counterpart poison/fire type after a fever.
And Anonymous asks:
When I think Ice/Poison, my mind first goes to pollution. Some sort of frozen sludge monster, perhaps, or a rotting corpse trapped under a layer of permafrost, its putrescence leaking into the surrounding environment.
Some interesting ideas! The cold/fever one could definitely be played with in some neat ways… maybe as alternate forms of a single Pokémon, even? If it’s a disease-based Pokémon, it might need to spread illnesses in order to keep itself healthy, which could make training one a challenge. The rotting corpse might be pushing it for a Pokémon game – I don’t know if Game Freak would go for that one – but the sludge monster idea sort of makes me want to see a Polar Muk regional variant.