I haven't heard anyone else mention this one. Every now and then a hero's skill reset cost will be negative. The first couple times, I didn't mind since I didn't need it, but recently I DID need it, so had to try it. Clicking it gave me free science points, and didn't reset my skills. I didn't try repeatedly clicking it because I didn't want to use an exploit on my current dungeon. I don't have any debug info or screenshot, but I'll try to get one if it happens again. The last character that it happened with was Gork.