Champions,the gravy of the basement

In the biding of Isaac, champion is the term used to refer to enhanced versions of enemies that appear randomly during the game (Just like almost every single thing). They add variety and a little extra challenge thanks to their different look and stats.

Champion enemies are similar to regular enemies, but they are easy to identify because of their distinct coloring, wich ranges from girlish, (seemingly) harmless pink to light absorbing, pure-evil black. In some cases the size is different too.
Champion Fat Fly and regular Fat Fly,
notice the difference in color and size. Champions are special not only because they're harder to find and are of a different color, they also have different characteristics that make them unique. Simple things like dealing more damage and taking more punishment before dying are the most usual thing when it comes to this guys but they can also have a different speed, be bigger or smaller (as mentioned before), shoot bigger bullets and many other things.

While it is random, there are things that influence the spawning of these exotic-colored creatures.
In each room of a level the game places a quantity of enemies, rocks, poops and other stuff to add flavor, once those things are chosen the game proceeds to decide what variation of it to put, and with some luck a champion might be born.

Once the choice making process is done it stays that way, except for enemies and some special poops. Wich means that if you run away from a room without killing all enemies, what was once a simple Maw could now be a blue Maw.Also, once you complete the game 6 times champions will be a more common occurrence.

Oh, and this also applies to bosses.

Yeah, it shouldn't be that big of a surprise, you most likely found one unless you haven't played much or you just were very lucky, specially if you have the Wrath of The Lamb DLC installed.

Champion versions of bosses are just what the name says, bosses that happen to be champions. This means that, just like any other champion, they have a different color and buffed stats. But bosses tend to have more noticeable changes than simple enemies (For example, spawning different enemies or having an exact duplicate helping them) and their variations also have disadvantages. Greenish-black Gurdy can only rely on her flies and blue Larry Jr. is slower and needs to take more damage before splitting, just to name two.

Some bosses have more champion versions than others (The maximum being 2), but almost everyone has a champion if you have the Wrath of The Lamb DLC. Some are harder to find than others, wich can make beating all versions of all bosses take a long time, thankfully the items they leave after dying aren't influenced by the version of the boss you fight.

While their existence seems like another threat to your live while you explore the dark depths of the basement,you can actually take advantage of this. Everytime you kill a champion* they drop something like a coin, a bomb (This includes troll bombs) or even a chest.
And taking into account that the enemies in a room respawn if you leave unless you kill every single one you can use the information in this guide to follow a simple 5-step plan that will make your life easier:

• 1: Get an item that grants you permanent explosive shots like the fetus or IPECAC
  
• 2: Go to a room with multiple enemies that are easy to kill, like maggots
  
• 3: Carefully kill every single champion in the room(If they're all champions leave one alive)
  
• 4: Blow up a door and get out of there
  
• 5: Lather, rinse and repeat

It's a long and boring process, but if you have patience it allows you to retrieve health, open up all doors and become a wealthy boy (A crying, scared little boy, but a wealthy boy nonetheless).
In fact, if you really have the patience and time needed you can do it until you get enough life in soul hearts to make mom look like a wimp in comparison. You must also take into account that all soul hearts past the twelfth will still count, but you won't be able to see them, so you'lll have to keep track of how many you have.

*If the enemy is above a hole when they die, they wont drop anything.

The term non-champion is a non official term used by me to refer to enemies that may be confused with champions but aren't.

An example of a non-champion is the Fat Fly,wich is related to the Pooter but isn't a champion of it.

Regular Host and regular Red Host,
notice the non-championship Just like a champion enemy,this guys have a similar look and behavior as another enemy and are distinguisable for their enhanced attack or speed. But unlike the real deal, this guys are actually a different enemy. That's why they have their own sprites and name instead of a recolor, and they have their own champions as well.
Another reason why you could mistake them for one is that they still can replace a regular enemy in some rare cases, and if they do this in a level where they shouldn't naturally be they'll drop something too.

Now that you know all what you really need about champions, you can go back to your naked-kid running-away-from-crazy-mother antics. Leave a comment if you wish so and tell me how to improve this guide if you think there's something missing.

Good luck, and stay gold!