- Alternative Character Interpretation: Twenty pages of Countdown are dedicated to reimagining Hastur, based heavily on the pre-Lovecraft work of Robert Chambers, The King in Yellow. note
- Broken Base:
- After receiving a lot of complaints that Delta Green was too "Americentric", Countdown expanded to foreign agencies and added two mythos-aware groups, PISCES of the United Kingdom and GRU SV-8 of Russia, with Targets of Opportunity adding M-EPIC of Canada. A discussion erupted if more important nations such as China, France note or Japan should get their own mythos aware groups? Or expanding outside MAJESTIC-12 and Delta Green was too much?
- Wiping out the old conspiracy groups. The writers felt that the old books relied on too many conspiracies and that a fixed metaplot would be too static (one creator even said that "You should have destroyed them by now"), so most of the old antagonists got destroyed (Majestic got taken by Delta Green, Stephan Alzis disappeared from the Fate, the Cult of Transcendence collapsed beneath its own weight, and the Karotechia was wiped out in a joint assault by DG, MJ-12 and SV-8). While the new Handler's Guide was rich in content it lacked new antagonists to fight. The Kickstarter for The Labyrinth, a new sourcebook containing new enemy groups, either solved this problem or made it worse by locking behind a paywall.
- Fall of DELTA GREEN and its GUMSHOE system brought some discussions: which system is a better for the Delta Green setting? The Basic Roleplay-inspired D100 system that the standalone game uses or Fall's GUMSHOE system? Some fans of Gumshoe were disappointed that the system was only going to be used for a Vietnam game, while the D100 system of the standalone was intended for all eras of play. Some others think that Gumshoe, with its simplified combat system compared is a bad fit for a game set in the Vietnam War, where combat will be prevalent, while the standalone's D100 is much more developed and tactical in that regard.
- Fanfic Fuel: The introduction of PISCES and GRU SV-8 in Countdown opened the doors for the fans creating their own groups. Adam Scott Glancy even wrote on guidelines to create your own group, with recommendations of history, themes, modus operandi and ways to not create something too cliché, generic or unrealistic.
- There's DG fanfics on DG ops going around North America.
- Friendly Fandoms: With Unknown Armies, as they share both themes and writers. John Tynes was the original mind behind the first Delta Green scenario Convergence and Greg Stolze would later write for the Standalone version of Delta Green; while thematically they share a hidden occult world, gritty and grim ambiance, destructive magic and the new Sanity Meter of the 2016 standalone Delta Green can be seen as a straight-up adaptation from Unknown Armies.
- Magnificent Bastard: Stephen Alzis, The Spook that governs The Fate. Turned up apparently ex nihilo in 1951 to control all organized crime of New York without begin discovered. He frequently outsmarts Delta Green, escaped death fifteen times (including multiple air crashes), and seems eerily close to being omnipresent and omniscient to the point that he simply doesn't worship any Great Old Ones or Outer Gods. As he says, "Does the carpenter care what color his hammer is?" He may or may not be an avatar of Nyarlathotep. He is, canonically speaking. Sort of. In the first sourcebook, he was also the only important NPC without a stat block because, as the description says, "Stephen Alzis is many things. Vulnerable is not one of them."
- Memetic Badass: RHINO teams, a fan-made resource for a team of highly armed special forces teams that the Agents could call for when they need some extra damage, they could best be seen as walking natural disasters that casually uses explosives and mortars, use them for when you want whatever you are fighting to turn into a fine mist. Just think of a cover story for the meteor strike that's about to happen.
- Paranoia Fuel:
- Just the idea of a black ops agency/unit fighting against alien/supernatural threats.
- And there's the idea that friendly assets/units can be turned by the same threats.
- There's also the problem of fighting human factions that want alien/supernatural tech.
- Take That, Scrappy!: In the 2016's splatbook, the not-so-liked Cult of Transcendence falls under its own weight and implodes. It's quite funny to see an all-powerful organization that was a threat to the whole of human society be destroyed like that, extra hilarity points for when you realise Delta Green — which mostly didn't had any clue of the existence of the Cult, acting as a Spanner in the Works when crossing with them — had nothing to do with their fall.
- Schedule Slip: The Cult of Transcendence first appeared in a paragraph in the 1997 sourcebook where they were annouced to appear in the next book (that would later become Countdown, released in 1999). The Cult of Transcendence would only be released in the sourcebook Targets of Opportunity in 2010!
- The Scrappy: The Cult of Transcendence is not well-regarded by fans. As its writing is seen as inferior if compared to other groups, sometimes hard to tie with the Delta Green metaplot (Even harder that they aren't known by any of the other factions so they can seem as Alien Space Bats), they're seen as too bloated (the Cult is formed by sub-cults which are formed by more sub-cults), and grotesque for the sake of shock value. The group was first accounced in the first sourcebook in 1997 and not released until 2010 with Targets of Opportunity, resulting in many fans thinking They Wasted A Perfectly Goodplot of the original premise of "Occult secret societies influencing politics on a global scale". In the new splatbook they became footnotes, after they were destroyed itself by too much infighting while some sub-cults became independent, quite a contrast with the quasi-omnipotent organization they were originally written as being. Some fans think they're represented better in The Fall of DELTA GREEN where the game focuses on its sub-cults and the Sees instead.
YMMV / Delta Green