All of the Seven Deadly Sins mini-bosses have an unique sprite not seen in any other enemy in the game... All of them, except Sloth, which is just a lazypalette swap of the Globins! That's a subtle, yet incredibly clever and ingenious joke.
Also, the worms he spawns that are usually pretty fast when charging are slower than the rest. They're lazy.
This has become even more plausible with the upgraded Sins from Wrath of the Lamb. Each has a disturbing new design... except Super Sloth, who's just a reskin of the Glazing Globins, as regular Sloth is to regular Globins.
Another of the Sins, Wrath, only attacks you with bombs. He can be damaged by these bombs, which doesn't seem to make a whole lot of sense... except that angry, or wrathful, people often do things that end up being self-destructive.
Similarly, Pride ends up using troll bombs a lot while also being resistant, if not immune, to their explosions. No wonder he's prideful; he can't be hurt by his own splash damage, so he uses it liberally.
Pride's other main attack is diagonal lightning beams, which you won't be in any danger from if you're attacking him optimally — but if you do get forced out of position for some reason (whether due to troll bombs appearing in your face, not being able to keep up with Pride's movements, your own items backfiring, or something else), you can get hit by the lightning without being able to retaliate (unless you have an item that defies the usual Denial of Diagonal Attack you're typically stuck with). Pride's only two attacks are randomly-spawned troll bombs and diagonal lightning beams, so either he has you scrambling around and struggling to fight back or you beat the crap out of him without him getting anywhere close to getting a single hit in. It must take a lot of confidence to use an attack strategy where you either crush your enemy or get crushed yourself.
Envy, while being one of the easiest mini-bosses to manage due to only being able to float around in more predictable patterns, also drops very little worthwhile, often dropping Troll Bombs. Of course he'd be envious; you have tons of things he doesn't.
The familiar you get from obtaining the Cube of Meat can push your bombs around, which can often spell disaster for you. If you get three Cubes of Meat, he will get his own body and follow you around. However, he'll still push your bombs around. Getting the Fetus in a Jar item makes it so your only attack is bombs. It also gives you a top hat and a monocle, reminiscent of Dr. Fetus. Combining the resulting bomb-spam and Meat Boy will probably kill you, because Meat Boy will often push your own bombs back at you. Could this be Meat Boy trying to get revenge on Dr. Fetus?
Whore of Babylon transforms the character into a demon with high attack power, but only when you have only one heart — AKA when you are near death. ??? does not have regular hearts, ever, therefore having WoB always active. Makes sense, since he is a Dead Blue Baby, and therefore as close to death as possible.
This also applies to The Lost, who is basically a ghost/spirit. As a One-Hit-Point Wonder of a ghost who can't gain any hearts whatsoever, he is literally one mistake away from dying. A perfect fit for Whore of Babylon.
Look at the names of the playable characters: Isaac (a sacrifice to God), Judas (a traitor), Cain (a murderer), Magdelene (a whore)note Mind you, that reputation is undeserved, but most people don't know otherwise, and Eve (the first sinner). Says a lot of what Mom thinks of her kids, doesn't it?
That says more about what Isaac thinks of himself, given that the other characters are Isaac in various costumes...
Another Fridge Brilliance moment comes in the addition of Samson, a man who was given incredible strength by God, and used it to great effect. It seems he's finally snapped out of his depression. The Wrath of the Lamb update in general showed that God has finally stepped into the ring to try and help Isaac escape.
Judas starts with 3 pennies, which seems odd — it'd seem more appropriate for Cain to have them, right? Except the original Judas sold out Jesus for thirty (3*10) coins.
It's more interesting than just "cancer makes you sad". The Cancer trinket has a unique effect in that it increases your rate of fire, without counting as a rate of fire upgrade. This means you can have upgraded your rate of fire to the cap, and Cancer will still increase your rate of fire, implying that no matter how sad you are, cancer can always make your situation worse.
Dad's Key allows you to exit any room, including challenge rooms. Now we know why Isaac only has a mom.
May fit under Fridge Horror, but ??? starts off with "the Poop". At first, one would assume that this was purely because ??? is a Lethal Joke Character, so he starts out with the joke item. However, when someone dies, the muscles within their body relax, resulting in a post-mortem bowel evacuation. ??? starts out with Poop because that's actually all he had!
The Whore of Babylon is a curse effect when you drop to half a heart. When Eve ate the fruit and became the first sinner, she was cursed by God and cast out of paradise; this is why Eve in game has to carry this curse no matter what.
Envy has a distinctly trollface-like smile, and he also often drops troll bombs on death. Perhaps trolls are envious of what other people have?
The Steam Sale, seemingly a very useful item, looks like some blatant butt-kissing. Once you've gotten it on The Womb or later, you realize sales sometimes come infuriatingly late.
If you manage to take the Steam Sale to the Blue Womb's shopnote which Greed will never spawn in, though, you might find yourself taking advantage of a sale at the last minute.
All the trinkets you get from beating Blue Baby with a certain character is something they've lost! Isaac has metaphorically lost his head, Cain is missing an eye, Judas lost his tongue after his betrayal of Jesus Christ, Maggy has lost her faith, Eve's bird has lost its foot, Blue Baby has lost his soul, and Samson, in the Bible, had a lock of his hair cut off, which made him lose his strength!
Also, when you think about it, Isaac being a sacrifice for his mother means he's most likely thinking about being killed by his mother, and thus decapitation. Also, the head joins you like other, dead or imaginary, familiars.
This is continued with the items you get for beating the Lamb in Rebirth, where these items were moved. Azazel's unlock, though, doesn't make any sense. This is because this is unlocked through the Sheol path. However, if you beat ??? as him, you get Abbadon, which is a representation of the entrance to hell. So, if you take the Cathedral path, Azazel has lost his way home. Isaac's item was changed to the Missing Poster because he "lost" himself. Lazarus's item, the Pandora's box, doesn't make sense because Lazarus was one of the people whose life was touched by Jesus. Lazarus was essentially pure, of course his item would be pure evil and because of that, his item doesn't make sense. None of Eden's items make sense because Eden isn't human. The items don't make sense because they wouldn't be recognizable. And to top it all off, The Lost's items for beating Satan, The Lamb, and ??? are all things that The Lost has lost. His mind, his body, and his soul.
Looking closely at Larry Jr. reveals that it's constantly crying. And why not? Its parents were killed back in Super Meat Boy.
Why does having flight allow you into a Curse Room without taking damage, but still hurts you on the way out? It's because the spikes are facing into the room, meaning that Isaac must prick himself trying to squeeze his way back out!
"Locked" characters are tied up, so when Isaac "Unlocks" them, he saves them. He saves a sibling and wishes them luck before trying to survive!
Lust's only attack is chasing after you, which makes perfect sense. Lustful people tend to chase others.
Rebirth adds a secret character, The Lost. The only way to unlock this character is to die repeatedly. In other words, lose the game.
And why can't this character gain any hearts? He's a ghost, so the food health upgrades just pass through him. He's already a soul, so soul hearts are ineffective, and since he's a holy ghost, dark hearts are rejected by him.
There are 31^8 possible seed combinations (excluding 5, I, O, U, and V). This turns out to be a Bible passage — Deuteronomy 31:8. What does the passage read? "The Lord himself goes before you and will be with you; he will never leave you nor forsake you. Do not be afraid; do not be discouraged.”
Why does the Lamb, a reference to Jesus, look demonic and get fought in a place lower than Hell itself? Well, it has been suggested that all of this game is essentially happening in Isaac's head, so the bosses appear as Isaac would view them. Isaac's probably too young to know much about the Bible or Christianity, but he knows that "God" is supposedly ordering his mother to kill him. Thus, it's not unthinkable that Isaac would view the Christian God (and by extension, Jesus) as a greater evil than Satan, hence the Lamb's appearance and position in the game.
It's also (more) likely that the Lamb represents the one that was sacrificed instead of Isaac back in the Bible. So it's fitting that it's the dark-side counterpart of Blue Baby, who is Isaac's dead body.
Why does the Bible beat Mom instantly? Well, she's obviously deranged and could be considered a Christian In Name Only, considering she only seems to follow her own bizarre interpretation of the Scripture. By showing her the Bible, you're revealing to her how off base she really is and she's unable to handle having her worldview shattered.
And a bit of meta Fridge Humor: the popular Twitch Emote "BibleThump" is Isaac's crying face. But in the epilogue, Mom dies from getting thumped on the head with a Bible.
Even the way you unlock him ties into this: you have to make three deals with The Devil in the same run, which involves trading your maximum life away for powerful items.
And even that ties in to making the game less fun. It's well known that devil deals are the (relatively) easy way to victory, and thus even they take away some fun because of their reliability.
Many of the Keeper's unlocks either benefit only himself or are just straight-up not very good. Then again, he is pretty much a playable Greed, and given Greed's tendency to be, well, a greedy jerk…
Building on this, The Keeper and Greed are, pardoning the pun, two sides of the same coin; a collective representation of one of Isaac's traumas like all other characters based on distinct states in Isaac's life or death. In this case, how he felt when his Mom took all of his things away. The Keeper as a player character and when referenced in items, still cries like any other version of Isaac because he lost all the toys he had made to keep the stories his dad told alive in his mind despite how much he pleaded with his mom. Greed, meanwhile, is his anger at having been stolen from despite those protests. His desire to not just take those things back, but take even more than he had to start with, is a natural trauma response in children having to deal with the idea of having lost nearly everything you hold dear. Ultra Greed's animations even play out like a child throwing a tantrum. But above all else, the ARG makes it clear that the one thing the Keeper and Greed want above all else is a voice. Specifically, a voice that people will listen to the objections of.
Gets even more layers in terms of the Repentance DLC. It can be argued that they represent not just Isaac's relationship to his material desires, but specifically the part of Isaac that he overheard his Mom saying he got from his father; an addictive personality that got hooked on games of chance. Be it a literal slot machine, or the thrill of a shiny new product in a store you don't know anything about. Most of Isaac's associated items being dice makes a more twisted amount of sense than ever with that in mind.
The final ending explains a lot about the story. It's shown earlier that Isaac's Mom has put up posters for her missing child, and she eventually finds his bones in the chest he's suffocated himself in. Now, Isaac's remains have clearly been there a long time, given they've decomposed already... why did it take her so long to simply look in the chest? The final ending explains this and Isaac's method of suicide: the chest used to contain their family pictures, with Dad burnt out of all of them. Of course a chest stuffed to the brim with terrible memories would be the last place Mom would look!
Why is Delirium immune to the Chaos Card? Because it already represents chaos itself, mainly Isaac's mind breaking down.
Similarly, The Beast being immune to the Chaos Card could play into its existence as the Beast of the Apocalypse. As it represents the chaos that would ensue by bringing about the end, it would naturally be impervious to such a card.
Related to the Four Souls card game: Why is Delirium's main gimmick as a boss that it will keep coming back every four monster cards when killed? Because until you manage to get it out of the deck, it's not actually dying; it's shapeshifting into other forms.
Isaac's Meaningful Name plays into the Maybe Magic, Maybe Mundane nature of the game's ambiguous canon as to whether Isaac's Mom is just a religious lunatic or genuinely hearing the voice of God/Satan, especially given the creator's Shrug of God and subtly dismissive comment about why Isaac's Mom might be willing to kill Isaac on God's say-so: it's a common atheist complaint that the story of Isaac's namesake in the Bible would ordinarily be regarded with horror as a story of a schizophrenic attempting to murder his son in a fit of madness. Instead, thanks to Christianity, we're instead told to revere it as an example of a properly intense reverence for God. This is especially poignant if one's aware of the various news stories where Real Life Christians have murdered their children due to fits of piousness-fueled insanity.
Credit cards let you buy things and pay for them in the future. That the Credit Card item lets you have things for free is foreshadowing that Isaac has no future.
Or it's someone else's entirely, in which case, you're just pulling money from their account without paying back.
Demon Beggars take your health and usually give you pills or syringe items in exchange. They're drug dealers.
Considering the truth of Isaac hiding in the chest, the murderous incarnation of Mom in his dream turns into a delirium-fueled interpretation of the thought "Mom's gonna kill me if she finds out".
Azazel is usually portrayed as either Satan or a demon working for him, so it may seem odd that in this he's on Isaac's side and not Satan's. However, if you look at the Apocalypse of Abraham it actually makes sense. For the unfamiliar, in the Old Testament, Abraham is told to sacrifice Isaac to prove his devotion to God. He prepares the sacrifice, then at the last minute, God sends an angel to tell Abraham to kill a ram instead of Isaac. The Apocalypse of Abraham also gives an account of Abraham's sacrifice (what he's going to sacrifice is not explicitly stated, but it's reasonable to assume that it's Isaac). As Abraham prepares the sacrifice, Azazel turns up and tries to convince Abraham to leave. Yahoel, an angel who is guiding Abraham, tells Azazel off then takes Azazel's angelic clothes and gives them to Abraham instead. Abraham then performs his sacrifice and receives a vision of heaven. If the two accounts are combined, this means that at the very least Azazel tried to save Isaac's life. YMMV on whether God simply changed his mind at the last second or planned it all, and whether Abraham actually intended to sacrifice Isaac, but it's possible that Azazel might have actually saved Isaac by buying time for God to change his mind and the messenger from God to arrive.
Sloth is a Palette Swap of the Globins, but lacks their distinctive quality of being able to regenerate after losing all their health. Of course he doesn't get back up after getting defeated, he's too lazy to keep fighting.
Alternate Cain gathers consumables and (in effect) items in a special inventory, and fuses them to craft items of his choice. Why is that his mechanic? Because his name is Cain, and it basically functions like the HoradricCube.
For a long time, it was accepted Fanon that Brother Bobby and Sister Maggy were likely Isaac's dead siblings, either from failed pregnancies or abortion. Edmund later Jossed this theory. But remember that Isaac's uncle is named Bob and his mom is named Magdalene (Dad even calls her Maggy during the ascent to Home). They're not Isaac's siblings, they're the innocent child versions of the "evil" side of Isaac's family.
With the revelation that the entire game has been just a bedtime story written by Isaac and narrated by his father, this has an interesting factoid attached to it. This means that every single run, either failed early or won at the end, is in fact a story Isaac made with his dad's help. This helps neatly explain all the randomly generated levels, items, and bosses, as well as giving a reason as to why you have to unlock things - Isaac either doesn't get the idea for it until something in his story crosses his mind, or his dad chips in with suggestions.
With Repentance's ending, Isaac doesn't delve deeper into his self-hatred and dark thoughts. Instead, he returns from his imaginary world to face reality. He defeats his interpretation of his mother's hatred, and normally is forced to continue downwards into his imagination. On the floor, though, there is a guaranteed card drop of The Fool Card: "Where Journey Begins". Using this to break out of the path before him, he uses the Polaroid and Negative to face the reality of his life, and ascends from his imagination back to the real world, where the voices of his mom and dad echo. Isaac comes to terms with how he isn't evil, and isn't the cause of his parents' hardships — he forgives himself. Isaac has repented. He returns to reality in Home, where he confronts the source of the problems — Dogma. The religious broadcasts and crazed televangelist teachings that radicalized his mother and caused his father to leave, and the source of Isaac's hatred of himself and fear of religion. The root cause to the entire story.
Why can the Corpse only be accessed by using the Knife Pieces to kill Mom's Heart early? Well, let's think. On this path, Isaac puts together a weapon that ends up drawing Mom's ire, enough to make her try and kill him when he gets the second piece. And when he has the chance, he goes straight for the heart before she's able to get away. This could imply on the normal path, she has time to put her heart in a secure place in the Womb/Utero/Scarred Womb while Isaac needs to fight through multiple enemies and rooms first. But in Mausoleum/Gehenna, she has no such opportunity. Therefore, killing her heart early leads him to her Corpse, because he effectively stopped her from escaping after the first defeat. No wonder it makes her go ballistic in the Mines/Ashpit, and why she has different moves in Mausoleum/Gehenna — she has an Oh, Crap! moment and realizes he has something other than his tears to definitely destroy her, so she changes up in a desperate attempt to stop him. Hell, maybe the entire reason he goes on the alt path is because instead of just trying to survive, he genuinely wants to fight back against her and deliberately seeks out something to put him on even footing with her. Of course, this all relies on the symbolism of the Knife Pieces…
As an aside, why can't you access the Corpse on the regular path? Because by the time Isaac realizes he has to kill her, it's too late, she's already retreated into her Womb. And being a child, perhaps he doesn't think just using Mom's Knife or the Sacrificial Knife will work. For him, Isaac may think he needs something he puts together on his own to definitely kill her. Thus, for the alt path, it starts with her wielding a knife of her own, and it ends with him wielding a knife of his own.
The Book of Revelations symbolism in Repentance's final ending isn't restricted to the Beast and Ultra Harbingers. In Revelations, the Beast has an agent known as the "false prophet," someone who "had worked the signs by which he deceived those who had received the mark of the Beast and those who worshiped its image." Meanwhile, the encounter with the Beast is preceded by the embodiment of those who twist God's word for their own ends and end up hurting others. Dogma is the false prophet.
Dogma also seems to be Isaac's interpretation of The Dragon of the Apocalypse, the being who "gave [the Beast] his power, and his seat, and great authority." On top of it being the first boss of Repentance's final ending's Boss Bonanza, with it ending with the Beast herself, having it be the personification of insane telemarketers and the like makes sense, as it's what drove Isaac's mother to insanity and thus start the events of the game.
Greed's Character Blog containing tons of questions about Isaac's dad and asking where he (or anyone else) is gives off the impression that Isaac's version of Greed also encompasses his need to have his family back together. It also implies that this need is something he hates about himself, as since it's associated with Greed, it also means he thinks he's selfish for wanting his dad to return.
Credit to u/vissonie on reddit for this: "i'm pretty sure all the mom stuff gives range because shes so tall to isaac".
During the fight with Dogma, a loud, rhythmic thumping/banging noise can be heard in the background. People who are aggressive and fervent in following and teaching Christianity, like the televangelist preachers Dogma represents, are often referred to as "Bible thumpers."
Why is Tainted Jacob's Birthright effect affect Dark Esau instead of him, creating another Dark Esau? Because it's not Jacob's Birthright, it's Esau's, and stealing it caused the whole mess in the first place. Why would he ever think doing it again would make his situation better?
Why does Ultra Death have such a different theme from the others? For Famine, Pestilance, War, and The Beast, Isaac is facing down monsters like always. For Death though, he's facing down Death outside of his fantasy as well, being locked in the toy chest and all.
May overlap with Fridge Horror, but when you get to Home, getting lucky with the Everything Jar or looking through the files reveal that the door to Isaac's room is cracked, similar to how the game's intro described it. However, bombing the rug will reveal that there's no trap door, unlike said intro. The journey underground may not have been real, but the abuse Isaac suffered certainly was.
When you think about it the true story is a parable for the biblical binding of isaac, even if unintended. Isaac was the sacrifice of both dad, leaving the household with great regret but knowing he couldn't stay, and mom, clearly projecting a lot of grief onto the child even when he wasn't the cause. In the end, unlike the biblical story, no outside help ever came. Isaac was isolated from everybody but mom who put all his father's sins on him. Even if she didn't mean to she readily put him on the stone emotionally when he had no escape and nobody came to rescue him in time.
While not intentional, Edmund said it fits. While playing as The Forgotten, you can take a devil deal as The Soul that would normally kill them, then switch back to The Forgotten to stay alive. However, you can't use the soul until you find more soul hearts. In other words, you sell your soul to the devil.
Let's talk about Repentance's Golden Ending. Every installment since Rebirth has had what seemed at the time to be a True Final Boss. Rebirth with Mega Satan, Afterbirth with Hush, and Afterbirth+ with Delirium. What do all three of these bosses have in common? The endings you get for defeating them raise more questions than they answer. But what else do they have in common? Getting to fight them at all is largely dependent on luck. For Mega Satan, you have to encounter two Angel Rooms in a single run, which, before the Angel/Devil Room formula was reworked, was easier said than done. For Hush, you need to have a strong enough build early on to make it all the way to Mom's Heart/It Lives in 30 minutes or less. And for Delirium, you can either defeat Hush, or hope the portal to the Void randomly appears early. For the Beast, however, all you need to do (after unlocking the exit to Home, of course) is make it to Depths II with a single bomb. And upon defeating the Beast, you are treated to an unambiguous and positive conclusion to the story. So, in both the gameplay and the narrative, the Beast's route lacks the uncertainty that all the previous "final" ending routes had.
Mulligans will occasionally spawn in a room with fires in it, and almost inevitably they'll end up killing themselves by walking into it. They're too stupid to notice it's there, right? Then you remember that they're people who are being horrifically mutated into hives for insects, and it's clear from their sobs that they don't like it, and you realize that they're probably trying to commit suicide.
Same happens when they're left alone for a while, they'll just decide to blow themselves up.
Which begs the question of why their bomb-carrying variants want to blow you up too. Unless they're so depressed for their existence that they're taking you with them.
You'll notice that the bomb is jammed into their head. Perhaps that bomb has taken over their brain and wants to kill you?
Although, as it is likely that the Mulligans, along with all the other enemies, are actually Isaac, then killing him would be the only way to truly commit suicide and end their existence… The non-bomb varieties tend to run away from Isaac as well — like they don't like him much like themselves.
The corpse that's in both the shop and hidden rooms has an uncanny resemblance to Greed. At first, seemingly a coincidence. Then the fact that Greed only attacks in these rooms implies that for whatever reason, Greed is playing dead on the occasions he doesn't attack…
Also Fridge Brilliance because his name is Greed, and when he sells you things, he… you know… takes your money.
Which also explains why he has a higher chance of spawning when you've visited a shop before or have a large amount of money; he's trying to take more money from you than you could pay him by buying out his wares.
Just to drive the point home. In Rebirth, bombing the shopkeeper has a chance of dropping the Steam Sale, Greed's drop item. Also, having Infestation 2, which spawns friendly spiders when you kill something, will spawn a spider when blowing up a motionless shopkeeper.
Which makes it all the more satisfying to blow up the shopkeepers to get back at Greed for all those times he screwed you over.
There is a between-floor nightmare where Isaac is suffocating in a chest. Beating It Lives for the first time gives you an ending where you find ??? in the chest. ??? is dead. There are a few endings that imply that Isaac went into the chest. Do the math.
The Ankh item resurrects Isaac as ??? if he dies. One ending has him dragged into the chest by Mom. You work it out.
To anyone who gives Isaac cancer (a trinket, boosts tear rate) and decides not to swap it out when another trinket spawns: You gave a child cancer and neglected to cure it. You monster! This is all the more tempting, given how useful a more tearful Isaac is.
And in a cruel irony, the trinket's description in Rebirth is "Yay, Cancer!", reflecting upon how useful it is.
Similarly, The Curved Horn is a representation of Isaac being demonic or demon possessed. Keeping it over other trinkets means you want a demonic (possessed) child! You monster! Again, a very good item, as it increases your damage output considerably.
If it makes you feel better, it's pretty easy to see it as Isaac carrying around a tumor.
The fact that you could literally throw the Cancer or Curved Horn on the floor at any time may confirm the above. Seeing as how the only trinket you can't drop is the Tick, this makes even more sense.
The SMB Super Fan item basically turns you into Meat Boy. Meat Boy has no skin. The aforementioned item's icon is a circular saw blade. Thinkabout it.
In the final level, the Chest, you can't bomb your way out of rooms. Isaac couldn't escape the chest, no matter how hard he tried.
Items and their effects tend to get this way if you think about them. For instance, the "Wooden Spoon" or "Belt" items makes Isaac faster… because he's running from being spanked! "Squeezy" may have been one of Isaac's favorite toys, so it makes him cry more as he holds it and remembers the good times in life (which is why he also gets two soul hearts). This also means when you get a pill that decreases tear damage/speed/range, you've actually made Isaac take something that makes him feel better, so he's crying less… even though this is portrayed as a negative thing.
Think about it. A Tears Down pill is actually an antidepressant, so Isaac cries less; conversely, Tears Up is a depressant! What the Hell, Player??
Then again, making Isaac cry more means that he's more likely to survive. It's sort of like how making someone aware of how much shit they're going through would make them more able to deal with it in the long run.
On a similar note, Bad Trip is normally just some drug that hurts Isaac. But when he's at 1/2 heart, it becomes Full Health. Isaac's so hurt that giving him the Bad Trip drug makes him hallucinate and become more pain resistant, allowing him to keep limping along.
There is a "Max's Head" item that makes Isaac's tears bigger and more powerful… There's also a "Lunch" item that is a dog bowl with the name "Max" on it… no wonder Isaac's tears get stronger because of "Max's Head"… it was his pet dog!
Ipecacis a serum that makes you vomit. It was used to expel poison from the body; however, ipecac itself is poisonous and has many of the same side effects. Moreover, it has been out of use for nearly a century and it is in fact recommended to throw it away. Why would Isaac's mom still have this?
The familiars have names like Sister Maggie, Brother Bobby, and the like. Either Mom had multiple miscarriages/abortions, or this isn't the first time "God" demanded a sacrifice…
Many of the "Humanoid" monsters look like Isaac. Why are there so many of them? Unless "God" demands many a sacrifice…
The Disc One final floor is the Womb, which is basically Isaac's mom's womb. It's not as bad as it sounds, until you realize what sorts of things Isaac's mother actually has in her womb, possibly including a tapeworm, a fallen angel, or the physical representation of death, depending on the RNG's benevolence.
Not only that, but her womb is actually divided into rooms.
One of these rooms can be a library. Isaac's mom literally has a library inside her vagina.
There's also a boss there called Teratoma. Teratomas are tumors with human body structures such as eyes, arms, legs, and teeth, and are generally present from birth and can be passed on from mother to child. Let us remind you that you fight the Teratoma in The Womb.
Take a look at the remains from a destroyed pile of poop. It looks remarkably like a smiley face. Is Isaac playing with the poop and making faces?
Afterbirth gives us the Burning Basement. While the environment combined with the music is pretty awesome in itself, it does make you wonder — why is the basement on fire in the first place? Is Isaac's mom that determined to sacrifice Isaac that she is willing to burn the whole house to the ground just to take him down?
Why does Isaac start with a bomb? He's so full of self-loathing that in case he wants to die quickly, he can blast himself.
During the fights with Mom and Mom's Heart/It Lives, Mom keeps yelling "ISAAC!" Just the crazed bellows of a child murderer, right? Wrong. They're the desperate shouts of a mother frantically searching for her son, filtering into his Dying Dream.
In the Rebirth remaster, the vocals for her shouts have been changed to sound more panicked than angry, supporting this theory.
The final revelation of Isaac's death is pretty horrifying when you realize how long he must've been in the chest. One would at least hope he would've suffocated relatively quickly, but then one has to consider Delirium. Not the boss, but the condition itself. It can cause serious mental confusion and hallucinations, which can explain Isaac's Dying Dream, but it doesn't occur as a result of suffocation. Something that can cause delirium? Severe dehydration, which sets in after one to two days without water. Three to five days without water, and the skin will start to turn grayish blue. What color does Isaac turn in one of those shot in Ending 20? At minimum, Isaac must've been in that chest, slowly dying and hallucinating, for almost a week.
With the revelation in Repentance that the game isn't Isaac's Dying Dream and is in-fact a story he's telling with the help of his father, there's the worrying fact that his "death" in the chest and the subsequent discovery by his mother were part of said story. Combined with the fact that one of the few endings that show Isaac's mother in a positive light are the ones where she's searching for him while he's suffocating in said chest, there lies the implication that Isaac thought the only way his Mom would ever care about him again was if he died.
More like Fridge Sadness, but given that the final unlocked item of the game is Death Certificate, why should we assume the final ending — where it's said the whole game was a story — wasn't also in the afterlife? After all, Isaac goes to heaven in the end of his story… and what is heaven for Isaac? "Isaac lived with his parents in a house on a hill..."
The Keeper's Tainted version, the Miser, looks quite a lot like a playable Super Greed. He even attacks similarly, using a quad shot to start with and making enemies drop coins on death. With the Tainted characters hailing from a Bad Future, this raises a terrifying question — is the Miser a version of the playable Keeper turning into Greed, or a minion of Greed? This ends up turning every run as the Miser from a typical jaunt into the depths into a long and drawn out Last Stand where the Keeper, while still maintaining control of his body, rushes to take out as many monsters as he can before he becomes another monster for Isaac to slay later.
More like Fridge Sadness, but consider how The Lost's Tainted version, The Baleful, appears. He's covered in a dusty Cobweb of Disuse and has lost his Holy Mantle and Eternal D6, now forced to rely on Holy Cards for defense. How did this happen? Well, consider that one level transition involves the Lost speaking to Mom from the attic, and how Mom reacted with horror and sorrow upon finding Isaac's bones in one ending. In the Baleful's timeline, Mom buried Isaac, then likely moved out, leaving the house behind because of all the pain associated with it. The Baleful likely remained within the attic, left alone and forgotten, for an unknown period of time. It was long enough that he lost something intrinsic to his being and visibly aged over time. In a way, the Baleful is chained to the painful environment that was Home, much like how the Fettered is still chained to his bones even if the physical link is severed.
The Curdled, Eve's Tainted counterpart, has likely dialed up her Self-Harm tendencies farther with the Sumptorium. If Eve was masochistic but still wanting to live, then the Curdled must have become a mild Death Seeker, indulging in Bloody Murder and leaving herself very vulnerable to getting killed should an attack slip through and hit her. And consider how her Bloody Babylon form looks compared to Eve's Whore of Babylon — more bloodied and feral-looking, less like a cursed child and more like an enraged beast on its last legs. What could have caused the Curdled to reach this point?
Edmund has stated that the reason why there's piles of poop everywhere in the game is because Isaac has IBS. While the exact causes of IBS are yet to be discovered, studies have shown that trauma and major stress experienced in life can be a contributing factor to it, including childhood abuse and divorce. It's possible that the tragedies in Isaac's life caused an adverse reaction in his guts.
There's numerous flies and poop piles in Isaac's basement, the flies are enemies, and the poop is rewardable vandalism material. Wearing an item called skatole, which is poop, deters flies. Yet you can't just grab a poop pile and smear it over yourself.
Maybe the Skatole is a notably solid poop that Isaac can carry around.
What kind of shopkeeper locks the store so that customers can't come in unless they have a key? Talk about being bad for business…
Greed doesn't want ordinary customers. He wants customers so desperate that they will hunt down keys to get to him. You might as well ask why Greed sometimes tries to kill them.
Fridge Brilliance: if you expended a key to enter the shop, you would be more likely to buy something after entering, even if this thing is another key to replace the one you used. You wouldn't want the key to have gone to waste, after all.
On the other side of the coin, the shopkeeper could have decided to close down for good and locked the place up so folks would know there's nothing to buy. Isaac loses coins from buying things because he's too kind to just take them. Greed just randomly lurks in shops and secret rooms to steal Isaac's money.
The Forsaken. Why is there a posthumous version of a ghost?
Or maybe he's not the posthumous version of the Haunt so much as the "didn't bother to get dressed" version.
The Haunt is a natural ghost that exists for the normal reasons. The Forsaken is that ghost being forced back into the mortal world through ritual magic after being banished. Effectively, it's not supposed to exist anymore and is suffering damage as a result.
Edmund himself says that Isaac is Steven, yet Isaac is also dead in The Chest that he trapped himself in. How is that possible? Don't the two confirmations cancel eachother out? Or is Isaac so sad and miserable that even after he's dead, his body rotted and his bones turned to ashes that he's brought back to life just to suffer eternally in the future? My head hurts just thinking about this.
it actually makes sense. For the unfamiliar, in the Old Testament, Abraham is told to sacrifice Isaac to prove his devotion to God. He prepares the sacrifice, then at the last minute, God sends an angel to tell Abraham to kill a ram instead of Isaac. The Apocalypse of Abraham also gives an account of Abraham's sacrifice (what he's going to sacrifice is not explicitly stated, but it's reasonable to assume that it's Isaac). As Abraham prepares the sacrifice, Azazel turns up and tries to convince Abraham to leave. Yahoel, an angel who is guiding Abraham, tells Azazel off then takes Azazel's angelic clothes and gives them to Abraham instead. Abraham then performs his sacrifice and receives a vision of heaven. If the two accounts are combined, this means that at the very least Azazel tried to save Isaac's life. YMMV on whether God simply changed his mind at the last second or planned it all, and whether Abraham actually intended to sacrifice Isaac, but it's possible that Azazel might have actually saved Isaac by buying time for God to change his mind and the messenger from God to arrive.