A quick history, from the Bogologist Field Guide (4th Edition):

"Millions of years ago, Boglins crawled out of the bogs on Bogzania, their home planet.

It is believed that years of built up methane gas in the atmosphere on Bogzania made the planet increasingly uninhabitable.

Because of this, three brave Boglins ventured out into the universe: Drizoul, Vizlobb, and Dwizork.

Propelled by the same methane gas they helped 'release' into the atmosphere of Bogzania, the three Boglins blasted through the universe into uncharted territory.

They left a trail of noxious gas allowing other Boglins to follow them to whichever new planet they travelled to. And so they did."