Cap'n Crunch in the 70's had a toy that could be modified to hack phone call lines.
Free whistles were given out in Cap'n Crunch cereal boxes produced a 2600 Hz tone
when blown (providing his nickname, "Captain Crunch"). This allowed control of phone
systems that worked on single frequency controls. One could sound a long whistle to
reset the line, followed by groups of whistles (a short tone for a "1", two for a "2", etc.)
to dial numbers.