A Hooloovoo was a humanoid species originating from one of the seven planets of the Sun-singers of Akhet. They attended the Festival of Offerings at the Pyramid of the Rings of Akhaten at least once. (TV: The Rings of Akhaten)
Behind the scenes
The Hooloovoo are a super intelligent shade of the colour blue in The Hitchhiker's Guide to the Galaxy by Douglas Adams. Adams was the script editor for season 17 of Doctor Who and also wrote three serials for the show.