Zygon McGillop

A Zygon was part of the group stuck on Earth. Their ship landed in 1562, but the group retreated into a stasis cube and stayed there until the 21st century, where this Zygon took McGillop's form.

Later, three of the Doctors erased the memories of both the humans and their Zygon counterparts, and peace was restored. (TV: The Day of the Doctor)