2. Replicators (Stargate)
The replicators were one of the main enemies in the world of Stargate. No matter what danger the team were facing, you could always count on the replicators being around somewhere just to make life more difficult. Essentially robotic spiders, the replicators track down new, advanced technology and take it for themselves. They consume all alloys and life that they can in order to create more of themselves, causing them to grow at an exponential rate and becoming ever more dangerous and destructive. So, Replicators as pets?? Not such a crazy thought considering they were originally created as toys/pets by an android. She ultimately lost control of them, however, which led them to destroy her planet and begin an age of destruction across the galaxy. Increasingly difficult to kill (due to a Borg-esque ability to adapt) these really arent things Id be able to let loose in suburban London! As further proof they are dangerous beyond belief-- while replicators were on set, Michael Shanks (the actor who played Daniel Jackson) had to be blindfolded at all times the cameras werent rolling due to his severe Arachnophobia and uncontrollable rage whenever he saw one!