Army of Meanwhiles and Neverweres

The Army of Meanwhiles and Neverweres fought in the Last Great Time War under the command of the Could've Been King. The Tenth Doctor mentioned this army as one of the horrors that would be released when broke the time-lock on the war, along with the Nightmare Child and the Horde of Travesties. (TV: The End of Time)

The Eleventh Doctor also referred to the stone-like echoes of the Daleks and Cybermen scattered around the Pandorica after the Total Event Collapse as "Footprints of the Neverwere." (TV: The Big Bang)

During the chaos of the Last Great Time War, the timelines of individuals, planets, and entire species were constantly being created, destroyed and re-written to further and stymie the advances of both sides. Details and histories of entire civilizations were being changed; personal timelines of important figures were being altered to change their loyalties, physical apperance or even erase them completely. Meanwhiles and Neverweres were the result; entities that still exist when the timelines that created them no longer exist. In some cases existing in parallel with the same entity of the current established timeline.