The Great Intelligence's MO

All of the Great Intelligence stories (I haven't seen the classic series ones, but I've read the Wikipedia articles, so please forgive me) have certain elements in common. Be warned, some of this may be spoilery if you haven't seen The Bells of Saint John yet.

The mirroring multi-nuclear host: In each story, the Great Intelligence has a multi-nuclear (that means it has more than one nucleus, or center) host that it possesses. In the classic series stories, it was those metal balls. In The Snowmen, it was the telepathic snow, each snowflake a nucleus. The snow actually had nothing to do with the Great Intelligence, it just happened, and the Great Intelligence took advantage of it. In The Bells of Saint John, it was the wireless routers and the Spoonheads. Both the snow and the Spoonheads appeared to be able to mirror people's thoughts back at them. It would soak up images and words from the surrounding people (like the girl on the book, the Doctor, the snowmen, and "that's the way to do it!") and copy them.

The beasts/foot soldiers: There were also the creatures that the Great Intelligence controlled to do its bidding. In the classic series these were the Yeti, while in the new series they were the snowmen and the Spoonheads. The Yeti were simply animals that the Great Intelligence was controlling telepathically, though they later turned into robots. The snowmen were controlled by the Great Intelligence because they were made of the telepathic snow that the Great Intelligence was already in control of. The snow was able to remember the shape of Dr. Simeon's snowman as a child. The Spoonheads were manufactured specifically for their purpose by Ms. Kizlet's company. They were controlled by the Great Intelligence simply because they were Wi-Fi connected, and the Great Intelligence was living inside the Wi-Fi.

The boss: This was the person that the Great Intelligence had contacted as a child and was connected to telepathically. I don't know who it was in the classic series episodes (I think there was something about a monk or a professor in one of the episodes), but in The Snowmen, it was Dr. Simeon, while in The Bells of Saint John, it was Ms. Kizlet. Each of these people became telepathically linked to the Intelligence as a child. Both of them felt very alone (Simeon didn't like the other children and Kizlet's parents had disappeared) and the Intelligence used this to befriend them and use them for its own purposes.