- "Something just moved past my leg!"
- ―Luke Skywalker
A dianoga was an icky, squishy, squoodgy, splodgy thing with tentacles and eyestalks. They skludged around gloopy places like sewers, garbage piles, polluted swamps... and sewers. I already said sewers, right? They really liked sewers. They squoomped and squidged along the gunk in the pipes, eating rotting bits of sludge and schmutz. Ordinarily, civilized beings kept well away from dianogas, but sometimes adventurers end up being thrown into a garbage chute or need to escape through the sewers, and they'll inevitably encounter one of the disgusting little pus-balls.
There persisted an urban myth that a dianoga could escape from the sewer system, crawl up a sewer pipe, and climb out of people's toilets... and although there was never a single confirmed case of this ever happening, sewage companies were forced to spend millions of credits on safety measures intended to keep dianogas out of residential pipes, and sensational authors made a fortune fear-mongering about little old ladies being assaulted in the privacy of their bathrooms.
Luke Skywalker was grabbed by a dianoga once on the Death Star. Dash Rendar fought one in the sewers of Coruscant. Anime and manga illustrators often drew disgusting pictures of dianogas and young Human girls engaged in unnatural acts; these were surprisingly good sellers.