In the Brothers Grimm tale "The Children of Hameln," the residents of that German city had a rat problem. A pied piper appeared claiming he could rid the town of their infestation for which the townspeople promised to pay him. The piper played his instrument and lured the rats to the Weser River where they all drowned. When he went to get paid the residents refused and the piper went away but would soon get his revenge. The pied piper returned while the townspeople were at church and began playing his pipe which attracted most of the children of the town. He and his hypnotic music lured them to a cave where they were never seen again.
Depending on which version of the tale you read, the ratcatching events took place either on June 26th or July 22nd. It's doubtful that most modern day pest control professionals actually celebrate Ratcatcher's Day.
WRAT is a Rock station licensed to Point Pleasant, New Jersey.