Get Smart - 3x15 - The Groovy Guru

A hippie disk jockey called the Groovy Guru (played by guest star Larry Storch) seeks to control the minds of teenagers through his radio show. This is a parody of the German folktale and Robert Browning's poem "The Pied Piper of Hamelin."
In 1997, TV Guide ranked this episode #67 on its list of the 100 Greatest Episodes.