Cap'n CrunchCap'n Crunch® is a breakfast cereal manufactured by the Quaker Oats company of Chicago. It is one of many sugary cereals targeted towards kids, and the majority of its TV advertising is aired during children's TV programming on Saturday mornings and weekday afternoons.
The cereal itself is a mixture of mashed maize (corn) and syrup, shaped into pieces that resemble barrels (of the sort that used to be a fixture of pre-ironclad sailing ships). The cereal is promoted by friendly old "Cap'n Crunch," a cartoon sea captain whose adventures revolve around the cereal. Cap'n Crunch's animated commercial adventures have given Quaker Oats the opportunity to spin off additional cereals based on the original, including Crunch Berries and Peanut Butter Crunch.
Cap'n Crunch cereal is a favorite choice for knowledgeable hackers and phreakers, due to an incident in the 1970s involving a toy prize that came with boxes of the cereal. Hacker John Draper discovered that a toy whistle packaged in boxes of the cereal at the time would emit a tone at precisely 2600 hertz -- the frequency used by the long-distance trunks in-band signaling to specify an idle condition. This would effectively disconnect one end of the trunk, allowing the still connected side to enter an operator mode.
This feature of the older phone call routing switches has long since been corrected, but it resulted in the Cap'n Crunch whistles becoming valued collector's items. Young hackers sometimes go by the handle "Captain Crunch" even today, as a result of this incident and 2600 The Hacker Quarterly is named after the frequency of the whistle.