The CharlieCard — which made its debut in 2006 — was named after the main character in "The M.T.A. Song." As the story goes, Charlie can't afford the new exit fare, so he gets stuck on the train forever.
Although the song was popularized by the Kingston Trio in 1959, it was originally a 1949 campaign song for Walter A. O'Brien. O'Brien was running for mayor of Boston with a strong opposition to the public transit fare increase. His campaign couldn't afford radio ads at the time, so he hired folk bands to play his campaign songs (including "The M.T.A. Song") from a touring truck.
The songs didn't exactly work — he was later fined $10 for "disturbing the peace," and ultimately lost the election.
Two undergrads have developed a wearable CharlieCard that is now available for purchase. Meet the Sesame Ring.