The first, but surely not the last...
My dress had gone missing, and I'd spent all morning looking for it. As a result, I wasn't able to get my hair and make up done, and I was wearing jeans and a t-shirt. It came time to leave, and the whole wedding party was immaculately turned out and looking lovely, and there was me denim clad with bare face and greasy hair - they said there wasn't time to sort myself out and that I had to go as I was.
For some reason, before the wedding, I was to be paraded around my home town on a float (I know - WTF?!), and the whole town had turned out and were lining the streets looking disappointed at the state of the bride.
It was awful!