" 'The babel fish' said the Hitchhiker's Guide to the Galaxy 'is small, yellow and leech like, and probably the oddest thing in the universe. it feeds on brainwave signals not from it's carrier, but those around it...' the guide then goes on to talk about
what it does with those frequencies and then it said '...the practical upshot of
this is that if you stick a babel fish in your ear you can instantly
understand all forms of language' it then talks about why the fish proves the non-existance of god and various other things that have happened as an indirect result of the babel fish's existance."