Airborne Algae Sack

Airborne algae sacks are a species indigenous to the planet Bespin. Given the term "sack", it is presumed that they are a race of gasbags, likely similar in physiological structure and appearance to the local Beldons, although since no known image of the species exists to date it is assumed that they are significantly smaller and more insignificant, due to the likelihood that they have not been warranted being important enough for images of the species to be taken or created by anyone. While they were likely only distantly related if related at all, it also indicates that they may utilize rethen gas to keep aloft.

Trivia
The name "algae" is a misnomer, as algae evolved on Earth, in a completely different galaxy. However, even on Earth the term doesn't refer to any monophiletic group of organisms and is used instead to refer to virtually any form of photosynthetic life other than terrestrial plants, so it might be valid for extraterrestrials as well.