The German name of the pied piper is "der Rattenfänger". The trick is that "Ratten" has two meanings : besides being the standard German for rats, it is a popular word for "kids".

Note that this lexical ambiguity between the many meanings of the word "Rats" was also the root of a famous case of severe mental disorder which was analyzed (and healed) by Sigmund Freud : Ernst Lanzer, the Rat Man.