Having found stuff yesterday about the Dance of Death, today's little corner of jollity is St Vitus Dance which affected Mediaeval Europe and may have been the inspiration for the story of the Pied Piper of Hamelin. Another name for it is St John's Dance. The story of the pied piper is, of course, famous as a poem by Browning
There's also a dance in Luxembourg which may be related - "Each spring, pilgrims flock to Echternach, Luxembourg, to participate in the town's famed "Dancing Procession." Taking two steps back for every three steps forward, the dancers painstakingly creep toward the grave of St. Willibrord, an Anglo-Saxon missionary who died in A.D. 739. Once there, participants pray for ailing relatives, for Willibrord is the patron saint of patients suffering from movement disorders."