Chris Higgins at Mental Floss has an educational and hilarious (How often do you get both?) look at the now 30-year-old practice of blowing into video games to make them work:
When things went wrong inside your NES, the problem was usually a bad connection between the cartridge and its slot. That could be due to tarnishing, corrosion, crud in various places, weak pins in the slot, or other issues. The symptoms of a bad connection could include the game not starting at all, the console showing a blinking light, or the game starting up with garbage all over the screen (below, a photo of Zelda II shows this form of startup glitch). To combat these problems, in the mid-1980s my friends and I somehow learned this secret: if we took out the cartridge, blew in it, and reinserted it, it worked. And if it didn’t work the first time, it eventually worked, on the second or fifth or tenth time. But looking back on it, I wondered: did that blowing actually help? And if it did…why? Was dust the culprit, and I was blowing it out of the cartridge? I spoke with several experts (who insisted they were not experts, despite their backgrounds) to find out.
Good thing Sony, Nintendo, and Microsoft have given up on physical media and moved to online distribution for everything. Wait what? They haven’t? Oh.