Approval of God: When In-Character twitter accounts became a growing trend among the playerbase, Funcom set up the Twitterverse Experiment, creating twitter accounts for various in-game characters for players to interact with.
The Danza: Annabel Usher is voiced by Annabel Scholey.
Executive Meddling: The development team is constantly poached by other projects, causing the game to be essentially undermanned and thus causing the long development cycles on new content. Some planned features like a tattoo parlour have had to be scrapped entirely because the the director doesn't have anyone left with the programming skills to actually implement them.
The Guardiansof Gaia have collectively earned the name Gollums. It began as common misspelling of golem and went from there.
The Patchwork Horror of the Filth Abnormalities event gained the nickname Teletubbie.
Mr. Reap, the Nephilim that unlocks your first ultimate ability. Name comes from his dialogue "Reap what you have sown."
The boss from the 2016 Anniversary Event was quickly dubbed the Hatekeeper.
In a case of the old name becoming the nickname, veteran players will still refer to Lore when talking about the renamed Legends in Secret World Legends.
This may due in part to the fact that if you're trying to search for guides to help find them all "secret world lore" will always be a more useful search than the alternative...
I Knew It!: The game has quite a lot of clues to future story developments scattered throughout. Players have done quite a good job at putting these clues together and guessing future storylines.
What Could Have Been: In early promotional materials, both Agartha and Shambala were presented as PvP maps, where players would fight over anima resources and powerful relics respectively, by release, Agartha had become the transit link between the various regions, and Shambala was replaced by the Fusang battleground.