Koffing
The Poison Gas Pokémon
Type: Poison
Official Registration #: 109
Entry: The body of this balloon-like pokémon consists primarily of gas bladders. These bladders are filled with a number of different gases, primarily hydrogen and sulfur dioxide, all of which are used in koffing’s various gas-based techniques. Due to koffing’s high hydrogen content, the pokémon’s body is extremely volatile and very prone to exploding at the slightest disturbance. On the positive side, its high sulfur dioxide content also means one can smell it from a mile away, rendering koffing’s explosive accidents perfectly avoidable … except for those who are audacious enough to train a literal ball of poisonous, explosive gases.
Weezing
The Poison Gas Pokémon
Type: Poison
Official Registration #: 110
Entry: The evolved form of koffing, by battle experience. In areas of high toxic pollution, koffing that feed in close proximity can merge to form systems of weezing. Although the norm is for two koffing to perform this feat, in areas with particularly high concentrations of toxic waste, triplet or even quadruplet weezing may occur. Yet despite this, they are still considered to be rare pokémon in the first region to have given birth to sentient garbage bags.
The Pokédex According to Bill 