New infrared imagery of Pieter Bruegel the Elder's Battle between Carnival and Lent, compared with imagery from Pieter Brueghel the Younger's copies, provides conclusive evidence that the great master himself transferred the composition to panel using pricked cartoons. These cartoons were later reused in his son's workshop for the making of the copies, one of which - an atypical version sold by Sotheby's, London, in 2012 - represents an earlier state of Bruegel the Elder's design. The other sorts of likely preparatory material made for the Battle between Carnival and Lent, now all lost, are also discussed. The second part of the article re-evaluates the main tendencies in Bruegel's preparatory work for painting in the light of new research and imagery. Indeed, the variety of underdrawing media employed in his paintings is greater than previously thought and includes the possible use of oiled charcoal in the Detroit Wedding Dance.