Zetheda was a planet once visited by the Tenth Doctor and Martha Jones. On their visit, they discovered that the whole planet was overflowing with unrecycled waste. The pair were then attacked by the Worgoth but were soon saved by the Ratlings - who sent the distress signal leading the TARDIS to Zetheda. The distress beacon also attracted the attention of the Optimi, a race of evolving humans who wanted to colonise the "paradise" world of Zethenda and destroy the Ratlings. Escaping, the Doctor, Martha and the Ratlings activated a terraforming device hidden underground that created a paradise landscape. In the end, the Ratlings and Optimi came to a compromise: the Ratlings would inhabit the wastelands, whilst the Optimi would live in the paradise they had been searching for. (COMIC: Waste Not)