You must have a Krawk petpet no other petpet will work.
Krawk petpet's are rather expensive but you can find them in the trading post or auctions.
They are unbuyables but if you have enough neopoints to trade for one at the trading post or auction, that is the way to get one.
1. Make sure you have no more than 3 neopets.
2. Give a Krawk PetPet to one of your NeoPets
(Any colors of Krawk petpet is fine)
3. Go to your Pet Status Page and Click On the petpet Krawk.
4. Rename the Petpet with an original name not currently in use.
(This will be the Krawk pet name when it changes form)
5. Take your petpet to the Fungus Cave
6. Let your petpet eat the fungus in the cave. It will then mutate into a Krawk.
Please note that If your petpet has been Zapped by the lab ray it won't be able to transform into a krawk :(
Other ways to get a Krawk as a pet is by adopting one in the pound, by user transfer, magical plushies morphing potions, transmogrification potions or if you are really lucky with the secret laboratory it might eventually change your pet into a krawk.
There is also an avatar for you to get once you have a Krawk :
To get this avatar simply visit the Fungus Cave while have a Krawk as your active pet!
Hope this guide was useful to you!