Chaucer depicted his Friar as a fun-loving playboy, which is an ironic divergence from the common image of monks as pious and self-disciplined. Rather than living his life among the poor, as was his oath, the Friar "knew the tavernes wel in every toun," and enjoyed singing and dancing while taking generous donations of silver from guilt-ridden penitents.
By depicting the Friar this way, Chaucer almost certainly made his readers laugh. The public face of 14th-century monasteries was of cloistered virtue and strict discipline. In truth, many monastic orders of the day had grown immensely rich from guilt offerings and tithes collected from pilgrims. By painting the image of a friar who is, in the author's description, a "lymytour," or beggar on behalf of the poor, and then devoting dozens of stanzas to his fun-loving ways and the glee with which he collected silver from parishioners, Chaucer achieved an ironic twist that is at the heart of the character's humor.
There is also a suggestion that the Friar has been made effeminate by his soft lifestyle. Near the end of Chaucer's description of him, after his disdain for lepers and general avoidance of the poor is depicted, it is said of the Friar: "Somwhat he lipsed for his wantownesse [wantonness]."