The hooloovoo is a super-intelligent shade of the colour blue. One was seen as a prism for Zaphod Beeblebrox's address upon stealing the Heart of Gold. On certain special occasions, such as the aforementioned Beeblebrox address, they will be refracted into a free-standing prism.
The hooloovoo demonstrate their dissatisfaction with the Universe by holding their breath until they turn a deep purple.
The hooloovoo appeared in:
- The Douglas Adams book The Hitchhiker's Guide to the Galaxy.
- The Eoin Colfer book And Another Thing....
One of their race is pointed out by The Doctor in the 2013 Doctor Who episode "The Rings of Akhaten".
In Season 3 of King of the Nerds the blue team named themselves "House Hooloovoo"
There is a software company Hooloovoo from Belgrade, Serbia, who used this and many references from the book to attract software developers with similar sense of humor.