Being an absolutely MASSIVE content mod for The Binding of Isaac, references to other works are bound to happen:
- There exists several references in Fiend Folio to the Madness Combat series:
- The Sanguine Hook is Sanford's meat hook, functioning as an active item with no cooldown that can be used to damage, weaken, and pull in enemies and pickups. Much like some of Sanford's more spectacular stunts with the thing, it also bypasses cover. Isaac also gains Sanford's bandana as long as he's carrying it.
- The Planetarium item Deimos, similarly, gives Isaac Deimos's hat and summons a familiar that uses Sanguine Hook for him.
- The Ascent-only enemies known as Mag Gapers, Mag Horfs, and Mag Clotties were all named after the Mag Agents, with all of them being stronger and larger versions of standard foes in their series.
- Another enemy, this time in the Corpse, known as Fingore, is a zombie that points at Isaac and tries to grab him. Fingore resembles the Unstoppable Nevadean Champion himself, Tricky. They also use sounds from the Grunts, further hammering in the reference.
- The name "Fingore" might also sound familiar, especially when paired with Scripulous.
- The Flavor Text for Clutch's Curse is "What if it was purple?".
- A Super Secret Room layout consisting of the Burning Basement tileset and two sets of Spicy Keys is internally labelled "Delightfully devilish", after a line from the infamous "Steamed Hams" scene.
- The hallway that forms the second-to-last room on the way to Knife Piece 2 sometimes generates in a layout added by the mod. One of these layouts is internally named "the hallway is aggressive.".
- A vertical 2x1 layout in the Womb is labeled "My deduction skills as a detective tell me he has quite possibly never -" (the last part, "had sex.", is cut off.)
- A secret room layout is labeled with Patrick Bateman's infamous "There is an idea of a Patrick Bateman" monologue. Yes, all of it.
- A room layout in Sheol is labeled as Master Skywalker, What are we going to do?, which contains 6 Psyegs, which promptly get killed by a Psy Hunter, referencing the infamous "Anakin kills the younglings" scene.
- The Warp Zone boss has the famous "WAAAARP ZOOOOONE!" scream during the Versus Character Splash.
- A promotional video for Reheated has Fiend KO'ing Isaac with a crowbar in the style of Team Fortress 2, before proceeding to hit the California Girls dance together with Golem.
- The Imp Soda is based on Crit-A-Cola, also from Team Fortress 2. Its Flavor Text, "Critical spit", likely references the "CRITICAL SHIT" meme.
- A soot-covered Fatty variant in Burning Basement is called Big Smoke.
- Meltdown, the Modern Horseman of Burning Basement, looks like a combination of War and Melting.
- Speaking of Nuclear Throne, There's also a secret joke option called Popo Modo, that spawns IDPD units, as well as Fish From Nuclear Thronenote , and also IDPD Gary.
- There's an Slim variant in The Dark Room called Slim Shady, that has a chance to spawn a Limb variant called the Red Hand.
- Several items reference Touhou Project and its various fanworks:
- The Dichromatic Butterfly gives Isaac Reimu's bow, shrinks his hitbox, lets him graze bullets for temporary damage boosts, and gives him a chance to fire Reimu's homing amulets.
- The Yin-Yang Orb is a trinket that gives an additional chance for homing amulets.
- The Chirumiru gives Isaac a soul heart, a damage boost, and freezes all enemies in a new room for 0.9 seconds.
- The Pot of Greed card comes directly from the Yu-Gi-Oh! franchise, complete with the same card back, text description, and effect (it spawns two cards, like a weaker Ancient Recall). There's even a small chance for the card announcer to whisper "What does it do?", referencing the meme of people asking what Pot of Greed does despite its simple effect.
- Speaking of trading card games, Energy Cards can be found and, like Pot of Greed, have their respective card back, they can also be found more often via the Energy Searcher trinket.
- The pill effect Melatonin (makes all enemies drowsy, eventually putting them to sleep and making them vulnerable to a single double-damage attack) uses this memetic snoring sound effect
when eaten. - The Organization bosses are inspired by the ghosts in Pac-Man, with them acting similarly to the four of them. Getting the boss badge of them requires you to use either The Gamekid or Power Pill to trigger the Pac-Man inspired transformation to chomp them down, with them getting scared like the ghosts do when Pac-Man eats a Power Pellet.
- Two of the enemies that can be found on the Cellar floor are called Homer and Marge.
- Two other bee-like enemies in Ashpit, called Ztewie and Briar (while not blatant references, especially Briar), are named after Stewie and Brian.
- An enemy in the Mines is called Thumper, referencing the tool of the same name from Dune.
- They also spawn enemies called Nubertsnote .
- Some of the new ghost enemies use voice clips of various ghosts from Luigi's Mansion.
- One of the two new horsemen featured in the mod, Pollution, is named after one of the modern-day horsemen featured in Discworld.
- An enemy encountered in the Mausoleum is Shi, whose name and design references Specimen 4. Thankfully, this one can't vore you like the original Specimen 4, otherwise this would be grounds for a Demonic Spider.
- When Golem picks up Technology, his face cracks open on one side, revealing a Terminator skull inside.
- On the Gehenna floor, there exists two enemies that serve as references to Doom, with these being the Super Shottie (named after the super shotgun, alongside referencing it and its meathook upgrade in Doom Eternal for its method of attack) and the Kukodemon (named after the Cacodemon).
- To detonate its planted bombs, the Quack enemy flips off the player in an identical manner to its visual inspiration, Dr. Fetus. Its name also serves as a reference to the ill-tempered kidnapper, being a reference to quack doctors.
- The Black Moon item serves as a reference to Lilith, as it not only gives Isaac a mask like the one she wears, but its activated aura spawns a red cross, not unlike the one she is crucified on.
- The 2.8 Spitshine update adds the Fuzzy Pickle trinket, which gives Isaac a small stat boost for every Shout-Out item he has.
- The Reheated Pizza item, when used on most characters, changes their head to be a mirror image of Peppino, the main protagonist of Pizza Tower. Equipping the item on Fiend and The Bastard turns their heads into The Noise and Fake Peppino's respectively, two bosses from the same game.
- Introduced at the same time as Reheated Pizza, the Pillar John enemy is named and loosely inspired by the character of the same name, who activates the timed escape sequences in Pizza Tower.
