In a similar vein, a former medium-sized client of mine had a retail / b2c product range launch and used identical placeholder EAN bar codes for each variant of the range. All the SKUs + their variants (around 200, from memory) had to be quietly recalled when retailers noted all the products had the same EAN - which turned out to be the 330ml Coke can that the designer had on their desk when they mocked up the bar code.
Edit: removed EAN.