We were talking about out pets and I told her about my cat and she said if we were to continue dating I would have to get rid of him because she doesn't like cats. For a moment I thought she was kidding because who would ask that of a first date (or any date). It became clear she wasn't kidding and was mad I wasn't taking her suggestion seriously. I didn't end up leaving, I was in the middle of my fettuccine alfredo and I wasn't about to scoop it into some doggy bag like some caveman. She took an Uber.
I haven't had many memorably bad dates, but that was the worst. Im willing to make certain reasonable changes for the right person, but cats are non-negotiable.