I had an interesting case once...
The company I was working for at the time had a large number of old windows XP machines that I was maintaining and one user had an issue where her machine would keep switching itself off.
After looking at the machine and reproducing the problem but finding nothing wrong with the software, I decided to pop the case off.
Spiders started running out from everywhere and the machine was thick with webs inside. By some miracle of engineering the fan was still turning but only just. Anyway, after half an hour with a toothbrush and a vacuum cleaner I finally got the damn thing stable again and handed the working machine back to the user.
Naturally, she wanted to know what was wrong with it and how I'd fixed it. So I told her that the machine was stuffed with webs and spiders. "Oh... is that an internet thing" She asked.
"No." I replied. "You literally had a PC filled with spiders."