Ok, so only one species this post due to a two-parter with classic series race the Sontarans. I suppose the clone humans with umbilicals at the backs of their necks might be new, but I think I'll just skip onto the next episode which featured among other things a feist lass who, on a very loose technicality, is the Doctor's daughter. But enough of that, let's look at some creepy aliens shall we?!
I have to say the team did a good job with the Hath race. Their look, while not completely original, was very definitive and interesting viewing. The bubbling tanks on their faces, while lacking explanation, did make an interesting dynamic, especially the added communication barrier it presented between them and the human characters. The idea of a seven day war was also intriguing, though there were some unanswered questions it threw up and I get the idea it could have made a brilliant novella but the author went for money and fame and handed it to Doctor Who...for which I can hardly blame them!
The Hath were a fish-like race adapted to a humanoid stature that had contact with the human race several thousand years into their culture. They breathed through a container of chemicals attached to their faces, possibly necessary due to their piscene nature. They were technologically advanced, with technology equal to or perhaps surpassing humanity's. One key element of their technology were progenation units which created a fully grown "child" from a DNA sample from one of their race in a matter of minutes. The process was interesting as it differed from cloning, not creating an exact copy, but a unique individual. This technology was shared with humans and used to rapidly co-colonise a planet. When an unexpected event seperated the two cultures the hath and humans fought a brutal war against each other. Due to the rapid progression of each race, coupled with massive casualties meant that within a week the two cultures had completely lost all trace of their original alliance and mythified what was only a recent past. Eventually the two races were alligned once more and colonised the planet in peace.
And there ya go - see you in a few weeks!