Goomba was the guardian of the swamp on Mars. (PROSE: The Heart of Mars) A "tree god of tremendous power and wiles" (PROSE: The Wickerwork Man) he resembled a piece of bamboo (PROSE: The Wickerwork Man, The Heart of Mars)
The Eighth Doctor believed that Goomba came from another dimension, and that he arrived on Earth at what humans called the dawn of time.
Goomba then landed in prehistoric China and planted himself in a forest of bamboo.
Millions of years later, Goomba was made into a wickerwork chair and shipped to a garden centre in Manchester. Peter's family bought the chair as part of a patio set and put it in their backyard. Goomba took possession of Peter's father and began amassing wooden objects. When Peter's father held a garden party, Goomba possessed the guests and began absorbing wood into himself. After a few days, Goomba had gained a large group of followers and a body composed of mostly furniture which as high as a beech. At Goomba's apotheosis, he planned on sacrificing all of his followers so that he could slip back into his home dimension. The Doctor lit a fire at Goomba's feet, destroying his body and releasing his hold on his followers. (PROSE: The Wickerwork Man)
During their trek through a swamp on Mars, Goomba appeared to Lora, Peter and Karl and warned them to leave his swamp. However, he relented and allowed them to continue when Lora revealed that they were looking for her Ma and little sister Hannah but advised them against waking the Ancient Gods. When the Anicents awoke and left Mars, Goomba realised that he no longer had a purpose and accepted Lora's offer to join her group. (PROSE: The Heart of Mars)
Behind the scenes
The character of Goomba also features in Something Borrowed and The Notorious Horkum Asylum in The Brenda and Effie Mysteries and Baker's End's Tatty Boggle.