I had an eccentric professor back in college who had a number of kooky mannerisms in the way that he talked and the way that he moved about the classroom. He was an amicable chap and clearly smart as a whip, but when he elicited laughter from his students, it was more often the case that we were laughing at him and not with him. Another defining aspect of this professor was the red sweater that he wore to class every day. Rain, snow, or bright sun. Spring, summer, autumn, or winter. Same red sweater. However, what struck me peculiar was a coiled up loose thread that stubbornly adhered to the front of the sweater. It was always there. Always in the same spot. How could this man be so clueless and not see the debris? I began to surmise that he either was the sort who just didn't give a rip about how he looked or he was some kind of alien robot.
The really irksome thing about this loose thread is that after a time, I kind of became fixated on it. He would be lecturing and telling us about the secrets of the universe and I was so locked into the loose thread that the rest of the world completely just vanished. Finally after three semesters of having this professor, I asked a buddy of mine what the deal was with the loose thread. He looked at me incredulously, like I had the intelligence of a turnip. He then said, "Dude, that loose thread cost him about 200 bucks. It spells out the name D-i-o-r!" Oh. At least there was now one less mystery in the universe.