WARNING: NOT FOR THE SQUEAMISH OR EASILY OFFENDED (thanks fresh.salty!)
Me and my girlfriend were browsing the fish in a LFS. There were some guppies that interested her, so I checked out a few other tanks while she was picking out the best of the batch.
I come back and she's still there, standing in the middle of a large puddle of blood.
I'll be as delicate as I can. It was that time of the month for her, and I figure her necessary feminine arrangements had sprung a severe leak. I tip her off, she looks down, comes to the same conclusion, and rushes out to the car to fix things; while I go ask an employee to bring me some cleaning supplies, then stand in front of the mess to help block it from view of any other customers that might happen by.
But embarrassment soon turned to confusion, when she comes back much sooner than I expected. She'd checked and double-checked. There was no chance the blood had come from her!
We couldn't figure out what happened. Was it already there? But a large puddle of blood is the kind of thing you tend to notice right away. Especially since this store had tanks at floor level, drawing your attention downwards, and we'd both looked at the one just inches away.
The employee insisted on cleaning the mess, and we were so creeped out we left without the guppies. We've referred to that LFS as "Bucket of Blood" ever since.