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My thread is more about bitcoin fact that you can check with blockchain explorer.
If you want to know more about Bitcoin fun fact that exists within the blockchain itself, you should check about BTC RPC explorer fun fact, the application also curating interesting fact within its app. For an example click the below image:

You can also see the full list without running the explorer by looking at their source code
here.
Block difficulty is retarget every 2016 blocks, but the first chance on block difficulty start at block #32256. Between block #1 and block #32256 the average block time was 16minutes. So retarget only works if block times are under 10minutes + difficulty above 1.00 !