In the 1974 Doctor Who serial Planet of the Spiders, Metebelis Three is known as the blue planet.
Planet of the Spiders is a six-part Doctor Who serial broadcast in 1974 during Jon Pertwee’s final story as the Third Doctor. The serial includes a powerful blue crystal from Metebelis Three, and its plot involves the Great One, giant spiders, and the Doctor’s confrontation with the consequences of earlier actions.
The story is sometimes connected with Pandora’s Box in trivia because its plot uses the release of dangerous power and the search for a potent object. It is not an adaptation of Hesiod’s myth, however, and the title Pandora’s Box does not belong to the serial. The exact phrase “blue planet” identifies Metebelis Three in the Doctor Who story.
Metebelis Three is also significant because the Doctor had previously visited it in the 1970 story The Green Death, where the blue crystal was introduced. This continuity link makes the planet’s description a more specific fact than simply calling it an alien world.