The Weed Creature is the main antagonist of the Doctor Who story "Fury from the Deep".
It was operated by Robert Pierson, Bill Straiton and Peter Day.
The Weed Creature was a form of intelligent seaweed located in the North Sea, which had been sighted as far back as the 18th century. It was parasitic, capable of attaching parts of itself to other lifeforms and controlling them, and showed an affinity to natural gas. It was also capable of emitting toxic gas, which stimulated its own growth.
The Weed Creature was disturbed by drilling operations by Euro Sea Gas and possessed the technicians who encountered it: Among the first to fall under its control were Oak and Quill, who acted as its main saboteurs. It slowly took over the entire drilling rig complex before switching its attention to the plant on the mainland, travelling along the pipeline and also sending its human agents to commit sabotage. It attempted to take control of the complex's assistant controller, Harris, by having part of itself placed in one of his files, but ended up infecting his wife Maggie instead. It succeeded in taking control of technical advisor Van Lutyens and ultimately the base's controller, John Robson, who functioned as its spokesman. The Weed Creature sought to gain control of the gas supply and dominate the British Isles, and possibly in time the world.
The Weed Creature was vulnerable to pure oxygen, to the point that those under its control needed gas masks to operate in oxygen-rich environments, so had Oak and Quill sabotage the complex's supply of oxygen canisters. However, it was also vulnerable to certain high-pitched sounds, including Victoria's screams, which twice caused it to break off attacks on the Doctor and his companions and also drove off the possessed Robson. The Doctor used a recording of the screams to fight the Weed Creature, driving back the section of the creature that attacked the complex and also sending it down the pipeline to destroy the nerve centre located on the control rig. All of those under the weed's control were freed and the Weed Creature was either destroyed completely or forced to retreat back into the sea.