I've had the random thoughts come up too... like this one recently. I just started a new job, and in the training session, we had the trainer, another new hire (both were male), and myself. I'm usually pretty guarded when alone in a room with only men, and I was that morning, too. But by the afternoon, I suddenly started thinking about them coming onto me and having a threesome with me! It dissipated fairly quickly though, and I went back to my usual guarded self.