Crytopcats are cute little 8-bit cats on the Ethereum Blockchain. The ownership for each of these cats is stored on Ethereum. Ethereum is a decentralised platform that runs the smart contracts, powering the CryptoCat ownership. Applications on Ethereum run exactly as programmed without any possibility of censorship or third party interference.
Just a really great idea and concept based on ethereum. Seems simple at a glance but in reality it opens our eyes to the possibilities of blockchain technologies and how they change the way we look at ownership.