1. Pierre et Paul are common characters in jokes.

2. They may also share distinctive ways of communicating, such as a repertoire of sayings and in- jokes.

3. Quirky elements like the reward of ‘Cake’ for success, Anthropomorphous storage crates, lonely machine-gun turrets and wry in-jokes.

4. The Boogaloo movement, which uses memes and in-jokes to incite real-world violence, indicates that social media-inspired terrorism has evolved and can coalesce quickly.