This should never happen

The mistake

A branch the developer assumed was unreachable carries a joke error message instead of real handling. A catch-all handler shows users a generic "something went wrong" apology and never logs or counts the actual error, so nobody notices that the "impossible" branch runs hundreds of times a day. It fires whenever an action is submitted twice, which is normal on the warehouse floor. Once the real error text is shown, the joke message reaches every user at once, and the only instruction it gives is to ask one named person.