Doctor Who Enemy Evolutions

The Macra are giant crab-like creatures who feed on poisonous gasses. They started out as a fairly intelligent species, hypnotizing a group of Human colonists who journeyed to their home planet and forcing them to mine gas for their consumption. The Doctor put an end to this enslavement, and he wouldn't see the Macra again for a long time. Over that period, the creatures devolved into mindless feral things with little intelligence left. This creature's redesign is slight and completely glossed over in the show. Essentially, it all boils down to going from large Papier-mché dummies to CG models. The Macra of the new Doctor Who look far more realistic, and their eye-stalks tend to be longer and thinner than those of their predecessors, although you could pass that off as evolution.    

These creatures played quite a landmark role in the Doctor's return to television. They mad appearances in the old show and were the first enemies that the televised version of the Ninth Doctor had faced off against in the reboot. In a way, much like Christopher Eccleston himself, they are underappreciated. After all, they were the ones who started the new series. These baddies actually experienced a sort of redesign during the run of the new show, going from something that looks a lot like a store display mannequin to a model that is completely identical to humans - like the ones in The Pandorica Opens. 

Yes, there are werewolves in Doctor Who. They aren't cursed humans or anything like that. Over time, the explanation for the cause of their affliction has changed along with their appearance. Due to budget constraints, the earlier versions of werewolves were just humans with bad makeup. The makeup grew a good deal more intricate during the new series, and a brand-new reason for werewolves was also introduced in the episode "Tooth and Claw." There, the Doctor claims that the werewolf is afflicted by an alien called "Lupine Wavelength Haemovariform," a strange race of creatures capable of transmitting their existence via bite.    

Second only to the Daleks, these baddies have appeared in countless of the Doctor's adventures. Their main goal is typically to turn all humans (and occasionally other species) into Cybermen. Since their inception, way back when in The Tenth Planet, these human-brained cyborgs have undergone a lot of changes to both their look and voice. Orignally, the Cybermen spoke simply with a higher pitched voice, bearing a strange inflection. Over time, however, that voice was turned more and more machine-like. Similarly - and probably due to a substantial budget increase - the appearance of the Cybermen also became more machine-like.