C. Norlander

"Norlander" was the name taken by a Zygon that had disguised itself as the sheriff of Truth or Consequences.

Kate Stewart met Norlander when she arrived in the New Mexican town. The sheriff showed her the ashes of some of the residents after a Zygon invasion. Later, she revealed her true form to Kate (TV: The Zygon Invasion) but was shot and killed by her soon afterwards. (TV: The Zygon Inversion)