After throughly "breathing" on these cartridges, and after a relatively short period of time, the game that would be using the cartridge would freeze up as the moisture ran out, and the TV which would be hooked up to your game will look psychedelic in 16 bit blocks.
For an idea of what these cartridges look like, look to your left. Occasionally there will be an ad for Busted Tees next to this definition and it will have a girl wearing a demin skirt and a green shirt saying Blow Me with a pic of a side view of a NES cartridge.
1998 (SNES)- "Donkey Kong Country isn't working again..."
1999 (SNES)- "Yoshi's Island is always working as usual ;D"
2000 (???) - "Screw this crap im gonna go play playstation"
Also known as "hippy crack".