I was taking a computer science course back in the late '80s in the UK. The course was a straight-to-masters 4 year undergraduate course. One of the requirements was that you were 'sponsored' by a company to get through the course, and IIRC they actually payed some of the tuition. You also had to present your thesis at the end of the 4 years to the faculty and representatives from the various sponsoring companies, a usually sombre and somewhat dull 2-day affair (6 students each day, of the 12 or so of us in each year).
Early in the final year, some friends and I were talking about the presentation, and relating how dull the previous year's was. Earnest undergrads desperately trying not to screw up, and impress the array of suits before them. During the conversation, we decided that it would be awesome if someone showed up in full evening dress.... and later on in the evening, somewhat worse for the wear, I proclaimed that if someone procured me an evening dress, I would wear it for my presentation.
Fast forward to the night before our presentation, after a less than stellar academic year on my part. A knock on the door just after I get back from a subdued night at the bar. A friend has found something for me to wear - not an evening dress, after all, but a dayglo orange halter top and mini-skirt. I figure, what the hell, as I didn't seem to have much to lose.
Next day, I'm on second. I show up early wearing an unseasonable long winter coat (it's may, and even in the north of England it's too warm for a long winter coat). I get a few odd looks, but I don't think anyone actually realizes that I'm presenting next that day.
First guy on that morning finished his presentation, and now it's my turn to present. I stand up at the back of the room, and take off my coat. The prof at the front who is MCing this shindig is the only one who is looking in my direction, and he said something like 'And now we have Mr. Pe.....'. His jaw dropped. I think it was the only time I ever saw him speechless. But then, he probably didn't see male students dressed in dayglo orange mini-skirts and halter tops every day, either...
I stood up, walked to the front, and gave my presentation as if there was nothing unusual going on. You know, I figured I'd already blown it so hard I couldn't screw it up any more. It was probably one of the easiest presentations I've ever done.
Anyway, a few weeks later I found out I'd passed, and I often wonder how much that last minute costume change worked in my favor... I did hear that the next year, the invitations discretely had 'business attire required' on them...