Amoeba

An amoeba was a kind of microscopic organism.

The planet Magla was in reality an 8,000-mile-wide amoeba with a crust-like shell. (TV: Destiny of the Daleks)

The Eighth Doctor and Charley Pollard encountered a large amoeba-like creature in the Divergent Universe. (AUDIO: Scherzo)

In the year 3110, the Eleventh Doctor saved the Musée d'Orsay from a giant amoeba that liked the taste of paint. (PROSE: The War of Art)