Each NFT has been randomly shuffled from the above things like Background, Fatcat, Nose etc.
The more things fall on each other from the rarity level, the rarer the NFT.
For example:
Does the NFT consist of
BackGround Rare + Nose Rare + Eyes Rare
it is quite unlikely, that such an NFT was generated again.
However, ​Does the NFT consist of
BackGround Common + Nose Common + Eyes Common
there is a very high probability, that this NFT will pass more than once. However, an NFT is never the same, because when creating it, care was taken to ensure that as many individual pieces as possible exist.