A customer, always arrogant and rude, never a nice word. Then she sent a document to me - I'm familiar with this kind of document, see it at least every two weeks for many years so I know what information has to be where and which kind of information was plausible on this kind of document.

She obviously forged the relevant data. I called the company who originally issued said document, yep: Completely made up data. Next day said customer called me and demanded when I would finally work with the document she sent me. I told her I knew it was altered, that I had already the original document sent on my way by the company originally issued it and that I already filed a criminal complaint against her. She was fined a few thousand bucks for forgery later on as it wasn't the first time.