WAY-BACK-WHEN:
Coding an inventory management system for the company that sold Cabbage Patch dolls, I slipped in a line that said if this was our test system (not production) and it was April Fools' Day, then the company name was "SYSTEM CRASH".
No one could see this but the coders while we were testing things. Once a year, we all got a good laugh and forgot about it until next year ...
...until management made the not-unreasonable decision to use the test system for end-user training.
Chaos ensued.
