Books and other teaching materials are shared at our school. All of our classes have coursebooks, but it's nice to supplement them with exercise from different books to break up the monotony of the same book day after day.
A few months ago, Incompetent Colleague commandeered one from our library and started calling it his. I really didn't care about that, because all of my classes were at levels that were either too low or high for it to be of use (I had used it with my advanced classes when they were at that level). However, now I have one class that the book would suit well and want to start using it again. I saw it on IC's desk and decided to make some photocopies from it today.
You can only imagine my surprise when I opened to a page and saw the answers written in! I flipped through a few more pages and saw the same. IC had written ALL the answers in the ENTIRE book so that he didn't have to look in the teacher's book!
I asked him about it, and he said, 'I did it so I wouldn't look dumb if I didn't know an answer. It's my book. I'll do what I like.' I responded by telling him that he didn't buy it, he took it from our library to use, and that it's the school's book for all of us to use. He said, 'Well, there's not much you can do about it now.'
I'm going to buy him a big bottle of correction fluid.