The alien thing you described in London comes from a really awful film
called 5 Million Years to Earth, circa 1965 or so. It did have some
pretty good concepts, though. That is, we are all descended from
Martian ant people and thus we are subject to becoming riotous zombies
because of repressed memories of a Martian war. I'm not sure what this
has to do with CPs.
It is quite possible that life in this section of the Universe all has
the same general make-up. It's also possible that the earth is a really
bad alien experiment. They seeded the earth with every bizarre species
of life they could get their hands on just to see what would happen. End
result? 20th century earth!
Now, assuming that CPs really are alien life forms, how could they get here?
Imagine, for a moment, a huge living organism somewhere in deep space. The
thing keeps growing and developing seeds by the quadrillions inside little
heat resistant pods. Finally, the space plant explodes and sends billions of
pods in all directions. Several pods land on earth, creating gaping holes
like Cape Fear, etc., when Pangea was still one continent. Eventually, the
pods exploded on contacting water - throwing zillions of seeds for hundreds
of miles around. This accounts for the wide variety of CPs across the earth
and the regional similarities between certain types of CPs.
The first CPs were very large and dangerous. They had traps that smelled
like dinosaurs and dinosaur food. Their first victims were
large dinosaurs. Over millions of years, the dinosaurs became extinct
due to predation by CPs. The CPs, no longer capable of catching large
meals, evolved to catch small meals. This explains why the dinosaurs went
extinct. Mammals and birds, not interested in dinosaur scents, thrived
and took over the earth. Insects, too primitive to discriminate taste in
food, fell victim to the CPs.
Now you know, as I know, the origin of CP life on earth.
---Steve