I'll go first: r/kitty. One of the hundred grillion cat subs back on Reddit, the culture in this one was you posted a cat picture, and the only word allowed in the title or in any comments or replies was "Kitty."
Someone is using that subreddit for covert communications, I just know it. Either on the level of "if u/PM_me_your_nostrils posts an orange cat, we attack at dawn!" or there's some steganography going on with the pictures, but that subreddit was too stupid to be as active as it was.
the stargate movie/show is "plausible deniability" soft disclosure of the real thing. they "hang a lantern" on this fact with the wormhole xtreme gag in the show.
Along the same lines, the X-Files was saturated with silly stuff and some real shit just to muddy the waters. X-Files producer had FBI and military advisors. But that's not the real conspiracy. The producer actually had a secret whistleblower advisor who was ex NSA who fed him real world storylines about dodgy shit the US govt was doing. Any time that they tried to censor the show, the producers were like "It's ok, the liaisons said to run it."