Well, in SHPS, I put some eastereggs into the commandline part (which I am quite proud of :D), for example quotes (which might not even be runnable, as one token cannot have whitespaces), commands which output quotes, config options which transform all stdout into 1337, and so on :D
At work, I usually write creative comments into the source code, for example, my PowerShell template includes at the end:
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######################### <º)))><,¸¸.·´¯`·.´¯`·.¸¸.·´¯`·.¸ So Long, and Thanks for All the Fish ###
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