Babel fish

The Babel fish is a fictional species of fish in The Hitch Hikers Guide To The Galaxy by Douglas Adams.

It is a highly improbable biological universal translator, a "small, yellow and leechlike" fish which, when inserted into the ear canal meant that the 'wearer' could "instantly understand anything said... in any form of language". This was both a useful plot device for Adams, who wrote on the subject that he always found the ability of all aliens to speak English very strange; and also the starting point for a joke about the existence of God.

According to the Hitchhikers Guide, the Babel fish was put forth as an example for the non-existence of God:

Something that perfect could only exist if there was a god to create it, so the Babel fish proved there was a god. Proof denies faith however, and faith is the standard by which we are to know God. Oops, says God, without faith I have no followers, and disappears in a puff of logic. (At which point humanity goes on to prove black is white and gets killed at the next pedestrian crossing).

The name refers to the Tower of Babel, which is a building referred to in the Bible. The story describes the supposed events which lead to God introducing different languages into the world.

The Babel fish inspired the name of the Babelfish online text translation service provided by the web portal Alta Vista. The existence of this online service "in no way proves or disproves God's existence on the Internet".