Vulpanan

Vulpanans are a sapient humanoid species from the planet Vulpana, known for their werewolf-like nature, which causes them to transform when under the influence of moonlight.

Biology
When in contact with the light of the full moon, they grow sharp claws and fangs, and become animalistic, savage, vicious, and extraordinarily hard to control, representing an instant danger to those around them. The effect can also be achieved by similar artificial sources of light, and even the image of the moon unnerves them. Silver bullets are fatal to them.

Captain Cook repeatedly described Mags as a rare specimen, but it's not clear whether he meant that Vulpanans are a rare species or that only a few Vulpanans can become werewolves.

Appearances

 * Doctor Who, season 25, "The Greatest Show in the Galaxy" (1988 - 1989)