You get a Krawk pet by taking a Krawk Petpet to Fungus Cave and having it eat the fungus there. Whatever color or style your Krawk Petpet is, that is what color/style your Krawk neopet will be. Krawk Petpets are only possible to buy in the Tyrannian Petpets Shop and not in Krawk Island as many people think. You will most likely find the Krawk Petpet in the trading post. They can cost up to nineteen million neopoints, since Krawks are a rare Neopets species, and are considered Limited Edition. They can not be made on Krawk Day unlike most other pets.
Note: If you use the Petpet Lab Ray to turn a Petpet into a Krawk Petpet, that Krawk Petpet cannot be turned into a Krawk neopet.
You can learn how to draw a Krawk Petpet here.