Darkwing is a minion, you give it to your pet and it will have its own little buddy
Now, if you want your pet to look similar to a Darkwing, try getting a dark Matter potion, they sell at the Millionaire Center
Also, I suggest looking at This site to help you out with Pet colors ;)
In order to change your pet's colour, you use a Potion or an Elixir on it. (Using an elixir will change your pet into that particular pet AND colour. For example, if you used a Dawn Fester Elixir on your pet, it would change to a Dawn Fester. If you used an Archan Elixir, it would change your pet to a Common Archan.) Potions only change your pet's colour, but most of them are very expensive. (Dark Matter Potion, for example, is 4 million sP.)
Darkwing is a minion, which is like a pet for your pet, but you dont have to feed it, train it, give it a profile etc...
To get different colors, you can use a potion. All of the popular subeta potions are really expensive, though, for example a nuclear potion or a reborn potion.
Basic potions/recolors are more affordable but less popular, for example the dawn potion or the field potion. One exception is the marsh potion, because it is only available in the Token Shop and the Potion Lottery... I think.
These will both change the color but not the species.
If you want to change the color and species, then you could buy an elixir. Those are only available for the basic colors. If you want to change the species and get an advanced potion, then you have to buy any elixir of that species and then use the potion.
Example:
Buy a for your Golden Kora, but you don't want a Spectrum Kora, you want a Spectrum Demi. You could buy any elixir of the species Demi from to . After that, you could use the and you would have your Spectrum Demi.
There are other special ways to get pets as well. Like for the Hydrus pet, you have to make a treasure map and complete a quest before you could pick a pet to turn Hydrus.
Another special color is Galactic. On the 6th and 7th of each month, the Coda Caves on Atebus will be available for you to bless your pets Galactic in. You do that by digging up gems in the caves for Itallo's quest, and giving them to him to bless your pet. (Or you can cheat and just buy them like I do. :P)
There is only one special species, that is the Aeanoid. The aeanoid doesn't have an elixir and isn't available when you pick a pet to adopt manually. You have to plant an and take care of it for about three days.. Then it will take over your active pet.
Something you could use to get your pets Dark-looking is a potion like the or the . Both of those look wicked. :D The makes your pet look dead.
Ask me any other questions.. I think I covered your questions and more. >_>
[flower=violette]