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Some of these are from the Python programming language. It seems they had a lot of fun making the language itself and hide quite a lot of random stuff amongst the more sensible parts of the language. However, as we’ll discover some of the additions have implications that explain why you don’t commonly find hidden surprises in the compilers and tools themselves.
There’s a few from the older machines where developers either wanted recognition for their work, or from companies trying to ensure their code wasn’t being copied without their permission.
If you have any more, let me know in the comments!