About weezing

Weezing alternately shrinks and inflates its twin bodies to mix together toxic gases inside. The more the gases are mixed, the more powerful the toxins become. The Pokémon also becomes more putrid. Very rarely, a sudden mutation can result in two small Koffing twins becoming conjoined as a Weezing. If one of the twin Koffing inflates, the other one deflates. It constantly mixes its poisonous gases.