Fatty

The Fatty is occasionally found in. It walks slowly toward Isaac. Occasionally, if Isaac approaches one, it will stop to fart, which will push him back without dealing damage. This will also push away adjacent enemies to a lesser degree.

Flaming Fatty
Flaming Fatties behave identically to regular Fatties but have a chance to leave behind a damaging flame upon death. Can release damaging flame by farting.

Pale Fatty
Pale Fatties can often be found in groups in. They behave like Fatties, but will also spit out 6 blood shots in all directions when farting. When killed, they have a chance to become a Blubber or a Half Sack.

Fat Sack
They are commonly found in groups of one to three, and can also be found together with Pale Fatties. Fat Sacks leap offscreen and attempt to land on Isaac, shooting 6 bullets in all directions and leaving a puddle of Red Creep behind when it lands. Like Pale Fatties, they have a chance to turn into a Blubber or Half Sack when killed. These monsters behave very similar to Leapers.

Blubber
Blubbers walk aimlessly around the room, randomly spewing a cluster of blood shots in all directions. When killed, there is a chance for it to become a Half Sack.

Half Sack
Half Sacks walk aimlessly around the room and leave Red Creep behind them.

Conjoined Fatty
Conjoined Fatties slowly walk towards Isaac and occasionally pause to fart out a line of damaging Green Creep. There is a chance that upon death, it will turn into a regular Fatty.

If killed while farting, the Creep line won't grow to its full length. It will instead stop spreading the instant the Conjoined Fatty is killed.

Blue Conjoined Fatty
Blue Conjoined Fatties slowly walk towards Isaac and occasionally fart out a homing Ipecac shot at Isaac. Unlike normal Conjoined Fatties, they won't turn into any kind of Fatty upon death.

Peeping Fatty
Peeping Fatties are an enemy introduced in The Binding of Isaac: Repentance. They slowly walk towards Isaac and occasionally fart out 6 blood shots in all directions. They are unique in that they have two indestructible eyeballs that float around them that are out of socket and attached by muscles.

Each eye generally prioritizes its focus on Isaac, but will occasionally become interested in something else, which could be an enemy, obstacle, or a collectible. The Peeping Fatty will sometimes begin perusing whatever one or both of his eyes have become fascinated with.

If both eyes are destroyed (using for example), the Fatty will become blind and wander around randomly.

Bloaty
Bloaties that, unlike other fatties, seem to be blind and do not chase Isaac nor target him. They periodically spit out a line of Green Creep and arcing projectiles in the direction they are facing or to its either side, horizontally or diagonally.

Bubbles
Bubbles slowly walk towards Isaac like regular Fatties and will occasionally fart sending out a burst of short range projectiles in all directions. Hitting a Bubbles will cause it to shoot a projectile in a random direction Upon death, they will burst into a geyser of projectiles that rain down in a large radius.

Shady
Shadies are variants of Fatties found in and. They follow Isaac at a faster pace than regular Fatties and have two attacks which they perform. They can shoot a large black and red projectiles towards Isaac which releases perpendicular shots to itself while traveling. These perpendicular shots accelerate while travelling. Upon colliding with a wall, the large projectile creates a ring of shots. Occasionally, Shadies may jump, causing lines of explosions in the cardinal directions.

Quakey
Quakeys are Mines variants of Fatties. They attempt to jump on Isaac, shooting out 8 rock shots when they hit the ground and causing rocks to fall from the ceiling.

Big Bony
Big Bonies walk towards towards Isaac, and occasionally fire a large bone projectile that bounces off of objects and can be destroyed.

Vis Fatty
Vis Fatties spawn with a Fetal Demon attached to their slit abdomens. The Fatty will slowly walk towards the player while the Fetal Demon occasionally lunges towards Isaac if he gets too close. As it is tethered, the Demon has a limited range of movement. Occasionally the Vis Fatty will fart, which briefly pushes the Fetal Demon away, giving it a substantial increase in range, as well as creating puddles of damaging Red Creep around the Fatty, the Demon and the cord that attaches them.

If the Fatty is killed first, the Demon will be broken free and continuously chase down the player similar to Gemini's Suture. If the Demon is killed first, the Vis Fatty unleashes a laser in the closest diagonal direction to Isaac. It will then fly backwards around the room diagonally, bumping off of walls and tall blocks all while continuously behind it.

Fetal Demon
Fetal Demons usually spawn tethered to a Vis Fatty's slit abdomen and occasionally makes short lunges towards Isaac if he gets close. They can also be propelled a longer distance when the Vis Fatty farts. If the Vis Fatty is killed they will chase Isaac similarly to Gemini's Suture. The only other place where they can be encountered is in the Mom fight in /, and is the only place where they are encountered alone.

Gutted Fatty
The Gutted Fatty is a monstrous variant of the Fatty that appears in. They slowly wonder around the room aimlessly and occasionally shoot out a pile of Festering Guts downwards leaving a trail of Red Creep. They can spawn a maximum of 3.

Every time a third of the Gutted Fatty's health is depleted, one of its eyes pops out and begins acting on its own. These eyes normally float around the Gutted Fatty they emerged from and block shots. Whenever Isaac walks too close to one of these eyes they will abandon their position and begin slowly chasing him instead. The eyes will return to defending the Gutted Fatty if Isaac walks far enough away from them. The eyes only die when the Gutted Fatty dies.

Upon death, the Gutted Fatty explodes into a massive shower of blood projectiles, similar to that of Bubbles.

Festering Guts
Festering Guts are spawned by Gutted Fatties. They travel around the room randomly in cardinal directions and occasionally spawn a Charger. The guts have to be killed to clear the room. They're never encountered on their own.

Tainted Faceless
Tainted Faceless walk towards towards Isaac while releasing 6 blood shots in a hexagonal shape rapidly. They essentially behave like Faceless with higher health and faster attack rate.

Stoney
Stoneys walk towards Isaac while blocking his shots. They stop and catch their breath after chasing Isaac for a few seconds. They do not do contact damage but will often push Isaac around. They are invincible, but die when the room is cleared, similar to the Death's Head enemies. Stoneys are unlocked by defeating The Lamb for the first time.

Cross Stoney
A Cross Stoney is a type of Stoney added in Booster Pack #5. These new enemies act like a hybridization of a Stoney and a Cross Stone Shooter; they constantly chase the player like a Stoney but will shoot 4 shots outwards vertically and diagonally like a Cross Grimace.

Cross Stoneys only appear in challenge #32 (Aprils Fool) as replacements to regular Stoneys.

Trivia

 * Blubbers appear to be headless Pale Fatties or, more accurately, headless Fat Sacks.
 * Similarly, Half Sacks appear to be the lower portions of Pale Fatties or, more accurately, the lower portions of Fat Sacks.
 * Conjoined Fatties and Blue Conjoined Fatties suffer the condition of polycephaly, having more than one head.
 * Conjoined Fatties and Blue Conjoined Fatties make the same high-pitched growling noises as Gapers instead of the lower-pitched ones used by other Fatties.
 * Stoneys look very similar to Stone Grimaces with bodies.
 * Stoneys make the sounds of a pitched-down Gaper.
 * Stoneys make the sounds of a pitched-down Fatty.
 * Cross Stoneys do not appear in regular runs; they only appear in the Aprils Fool challenge.
 * Antibirth developer Kilburn first revealed Cross Stoneys on the 1st of April for Booster Pack #5.
 * It was revealed on the 1st of April, and Cross Stoneys are exclusive to the Aprils Fool Challenge.
 * Blue Conjoined Fatties were redesigned to look similar to Hush
 * In Antibirth, Quakies used to have a face of a regular Fatty.
 * In Antibirth, Big Bony's bone attack used to be different - the bone was a lobbed projectile that created shockwaves in the place of its impact. Big Bonies also used to spawn in.
 * In Antibirth, Bloatys were known as Barfy, had a different appearance and were encountered in.
 * Vis Fatties look very similar to Exorcists.