Co-op babies - 2 are better than one!

This guide is aimed to those couples or groups of friends that want to try co-op mode, and for those that already play it but don't know how to maximize the effect of the baby in the run.

Before we start...

·To play co-op, you only need ONE copy of rebirth/afterbirth/ab+. Do not purchase more than one, since it's only local coop

·To play co-op, you need at least 2 controllers or one controller+one keyboard (2 keyboards are not adapted to play co-op sadly), up to 4 controllers. Best if those controllers are xbox controllers, but there are some others that may work fine.

·Coop-ing does not disable achievements.

·Have fun!

What is a "baby"?

When a man and a woman love each other so much... They may play Binding of Isaac together. Edmund made a co-op mode with babies as the co-op player to make them able to do so. (You can also play with up to 3 friends)

Some babies are "special". Special babies have extra bonuses, that may help Isaac or help the enemies. Most special babies are unlocked by each character, by:
-Killing Mom's Heart or It lives! in Hard difficulty (Apollyon does not unlock any baby doing so)
-Killing Mega Satan
-Earning all completition marks on Hard difficulty.

At the start of the game, you can choose between a random non-special baby or between several special babies. When a special baby dies, you can't choose that baby again. Babies may have up to 3 hearts, depending on your current health, but always start with one heart.

Which are the best special babies?

When you kill Mom's heart in hard difficulty with the lost, you unlock the -o- baby. This baby is immortal and may deal contact damage and apply contact effects with items like the virus, serpent's kiss, midas touch or E.colli. He can also pay hearts to a donation machine or a blood beggar freely.

Pros:
-Immortality.
-Contact damage
-Able to abuse heart payments.
Cons:
-Has no aggro - enemies ignore him.
-It becomes boring after a while.
Goes well with:
-Everyone.
-The keeper can trade one heart to get this immortal baby. He can get his heart back by any Hp up afterwards.

When you get all completition marks with Maggy, you get the Colourful baby. This baby heals instantly Isaac when coming into play. You can abuse this by entering, leaving, and entering again when Isaac is dealt damage. Has infinite uses as long as you are fast enough to enter and leave before getting hurt.

Pros:
-Infinite healing.
-You can abuse donation machines, blood beggars and, most importantly, sacrifice rooms.
Cons:
-Can die if you are not cautious or too slow.
-No effect on ???, Azazel (unless you have 3+ red hearts), Keeper
Goes well with:
-Everyone with 3+ red hearts. More hearts=Less chance of dying by mistake.
-Samson goes extremely well with him, as you can have at least 10 damage in every chapter by hitting yourself on purpose and then healing.

The white baby is the reward for killing Mega Satan with The Lost. When he comes into play, Isaac gets a white heart. Leaving with him also makes the white heart disappear.


Pros:
-You can come into play right before leaving a floor, to get a free extra heart. This can be done every time you finish a floor.
Cons:
-Its only use is that. Using it on combat is counterproductive.
Goes well with:
-Everyone, except the keeper.

The Magnet Baby is the best free baby. He can't shoot, but he flies and can pick up pickups and open chests.



Pros:
-Can pick up items that you may not be able to reach. Can also put bombs to pick distant marked rocks.
Cons:
-Can't shoot tears.
-Can't pick up items.
-Useless when Isaac has fly.
Goes well with:
Everyone except azazel, since he can already fly.


Always start a run with one of this 4 babies if you want an easier run. Other great babies to have are:
-the psy baby(free) that can shoot homing tears.
-the cy-baby(free) that shoots a laser randomly, as if having Tech.5.
-the blue baby or black baby, that start with an extra blue or black heart.
-the super greed baby that shoots coin tears that sometimes spawn a coin.
-the mort baby, that spawns 1 rechargeable fly like rotten baby.

Challenges

Some challenges are made way easier with a co-op baby, specially since babies can't be blinded:

Solar system: You get a shooting baby, but you lose one attack fly (specifically, the blue fly given by the item forever alone). It's easier in the long run, but may be frustrating for the Isaac player.

Suicide king: Play alone. This one is particularly dangerous in co-op, unless you lose ipecac.

Cat got your tongue: Shooting Guppy. Instawin with any baby.

Demo man: Harder in co-op than alone. It's fun, though.

Glass cannon: Harder in co-op.

Family man: The baby can shoot, but Isaac loses a familiar.

Brains!: Isaac loses one bob's brain, but you can now shoot through your co-op baby.

Onan's streak: Twice the possibility of dying. Colourful baby and white baby are great here, though.

The guardian: Play with -o- baby to have twice the damage and a lot more map control. Strongly recommended.

Pokey mans: Twice as much pokeymons are summoned. Also highly recommended.

Ultra hard: Play with colourful baby to make this achievement fairly easy. It's so powerful, it's even advisable to do it by yourself (entering with another controller when the room is empty and Isaac has lost health).

[Juani]

Is it possible to play WITHOUT babies?

[hidden.name.96]

can anybody help me? I know how to play coop with controllers but i don't know how to play as babies

[Donpompigordo]

@windows 98 Glad you are not having any financial issues. Hope you can try co-op soon.
@jmarshal74 Thanks! If you are striken with any doubts, I'll gladly answer them.

[Tris]

Very useful!

[Donpompigordo]

You can see if your controller can be adapted with xpadder or similar emulators, still. An used xbox controller may be around 5-20 bucks or so in a thrift store if you are tight on money.

[Donpompigordo]

You must have an xbox controller. Some controllers do also work fine, some do with xpadder, and some simply do not work. 2 keyboards are sadly not supported.

[Donpompigordo]

Not at all. The only babies that need ab+ are mort baby and apollyon baby (which are not game-changing). White baby and colourful baby do require afterbirth (the first expansion)
Co-op was also enabled since rebirth.

[Kindos]

does this require ab+?

[Donpompigordo]

Thanks, I'll edit the guide with that info.
Co-op mode doesn't disable any achievement. Feel free to play with anyone!

[Carbo]

And another 2 things:

First: When i used the Mort Baby on the challenge Solar System, He took my blue fly orbital (I don't remember the name) and spawned one blue attack fly (Like the Rotten Baby) So i saw him very OP

And second: Does the Co-Op mode disable achievements?