In the seventies John Draper aka "Captain Crunch" became a well-known phone phreaker [i.e. a hacker of the phone system] when he discovered that the whistle that came in Captain Crunch cereal generated exactly the right tone to convince the phone system to give you free long distance. Eventually the authorities caught on and changed the tone slightly -- the old tone still worked but now they could track people who were illegally using it. Captain Crunch ended up in prison, where he eventually survived by teaching hard-core criminals his knowledge of the phone system. Twenty-some years later he showed up in the San Francisco rave scene, a wild-looking man with gray hair and majorly fucked-up teeth as a result of his prison experience. He would stay up for days dancing and partying -- "high on the energy", he said -- and trying to seduce young rave boys.

(Source: 666.com/stories/john-draper.html