Could've Been King
From Tardis Wiki, the free Doctor Who reference
The Could've-Been King led the Army of Meanwhiles and Neverweres during the Last Great Time War. The Tenth Doctor described this as one of the potential horrors that would be released when the Saxon Master broke the time-lock on the war, along with the Nightmare Child and the Horde of Travesties. (TV: The End of Time)
While on the Crucible, Dalek Caan reminisced on "Could've Been Kings" (plural) tore apart his casing (PROSE: Dalek Caan) after broke through the time lock of the Last Great Time War to rescue Davros. (TV: Journey's End)
