Dianoga
Dianoga are a species of opportunistic, hermaphroditic squidlike, aquatic scavengers. Native to Vodran, a few of these creatures managed to stow away aboard spacecraft in larval form and established themselves across the galaxy in sewers and swamps. At least one adult dianoga lived on the Death Star in its trash compactors until the Death Star's destruction.
References
- Dianoga on StarWars.com