I got permanent damage on a CRT by playing with some magnets neat it. Never left them around it overnight or anything. They were the magnets from the magnetic beyblade arena lol. The sides of the screen got sort of more red. If bright colors, especially white, were on those areas for a long time they’d get progressively more discolored. It would fade back to its mostly normal dull red shade after some time without the bright white. So it wasn’t the worst damage ever, but it was definitely permanent damage and definitely noticeable.