Using a Capt. Crunch whistle, you could recreate the tones telcoms used to initiate long distance calling. Meaning you could blow the whistle and get free long distance. http://en.wikipedia.org/wiki/John_Draper

It's a plastic whistle, like the ones that were found in some cereal boxes forty years ago.

It emits a note at 2600Hz, which coincidentally was the frequency for carrier control on the Bell phone network at the time.

See: http://en.wikipedia.org/wiki/John_Draper#Phreaking

It's a reference back to John Draper's work on the blue box. You could trick AT&T pay phones into thinking you had deposited money by playing tones which were reproducible on toys that came out of Captain Crunch boxes.

In the early early days of telephone hacking (phone phreaking) a guy named John Draper discovered that the toy whistle found in a box of Cap'n Crunch cereal would emit a tone at precisely 2600 Hz. This frequency was used by The Bell System to issue call routing instructions. With it, you could make free long-distance calls around the world. Some via satellite.