Peanuts: It's The Pied Piper, Charlie Brown

It's the Pied Piper, Charlie Brown is a retelling to Sally by Charlie Brown of the story how the Pied Piper of Hamelin (portrayed by Snoopy as the Pied Piper Beagle) chased away all the mice (changed by Charlie Brown from rats because, upon the story saying that the rats fought the dogs and killed the cats, Sally is terrified of rats) from the city of Hamelin. The Peanuts kids substitute some characters, Snoopy being the Pied Piper Beagle with his contract being for a year's supply of dog food. Snoopy plays a concertina (squeezebox, with presumably David Benoit doing the honors). Instead of bringing the kids out of town with his music, Snoopy does it to the mayor and his assistants.
The special breaks Peanuts tradition in that it shows adults, who speak audible language (unlike most other Peanuts specials in which adults are only heard off stage speaking in "wah wah wah" sound of a muted trombone). The other good examples are the This is America, Charlie Brown miniseries, which portrayed adult historical figures alongside the kids, as well as "Life Is a Circus, Charlie Brown," which featured a talking circus announcer.