CryptoPunks

10,000 unique collectible characters with proof of ownership stored on the Ethereum blockchain in the NFT project CryptoPunks, which create by John Watkinson and Matt Hall. As long as they have an Ethereum wallet, anyone can claim CryptoPunk virtual characters for free. Since the ERC721 standard was not established at that time, CryptoPunks did not follow the ERC721 standard. Due to this limitation, its virtual characters are not entirely ERC721. Therefore, the technical standard for CryptoPunks to construct virtual characters can be described as a mixture of ERC721 and ERC20.