The Carnival is to invite in the Spring, and to scare away the Winter. In Ptuj there is a special version where the "Kurent" scares away the winter. It seems the origin of Kurent is lost in history, but the costume is really impressive:
I'd love to be in Ptuj for the Carnival. Apparently there were 10,000 people in this year's parade and there were 700 kurenti!