The Catcoin API is a Scratch currency, like Sipcoin, but easier and less, well, broken and obsolete. Not very many people use Sipcoin! My Sipcoin 5 project is based on Catcoin, so it will work better.
The song that plays when you hack this is by Rick Astley. Catcoin is made by me. I recommend using the original Catcoin API project as it is more up-to-date.