Megaluthian slimeskimmer

Megaluthian slimeskimmers were a sentient species. At some point in history they exploded the third planet of an unspecified star system. (AUDIO: Neverland)

Behind the scenes
They were first mentioned in the invalid Dimensions in Time, in which the Third Doctor stated that he should be taking it easy, not bounding around like some Megaluthian slimeskimmer.