Flower print dresses are absolutely gorgeous, but if those flowers are in the wrong places they can become nightmares. Think about flowers right on the nipples, or in this case, on the butt, making it look like you just had that time of the month. Either that or you sat on a bunch of knives. I'd be the guy who runs up to her to tell her there's been a horrible accident, only to realize my mistake. Now that's a nice meet cute.
It's on the very back of the dress too, so there's no way she'll ever know until it's too late. If this is a lesson for anything, it's to always check your backside before you leave the house. You never know what could be back there. People won't say anything either. They'll just let you walk around like a fool.