Wilkins
A Thief-in-training during the events of Interesting Times. He was in a group of apprentice thieves, who were being trained by Thieves' Guild president Mr. Boggis. Typical training consisted of lurking in an alley until passerby came by, and then bopping them on the head.
During Wilkins' training, Rincewind (who was still in shock from being transported over six hundred miles in two seconds by Hex) came by the alley, and one of Wilkins' fellows took the opportunity to attempt an Overarm Belter on the back of Rincewind's head. To the disappointment of Boggis, however, it was a horrible attempt at a Belter. He very politely got Rincewind back on his feet and then gave him a proper Overarm Belter, and then also demonstrated the incorrect Belter- also on Rincewind's head. Boggis then invited Wilkins (who was giggling at his classmate's discomfort) to have a go, but Wilkins also mangled it. Rincewind crawled away as Boggis then took the opportunity to demonstrate the finer points of head percussion on Wilkins.
As Boggis commented to Unseen University's Faculty (who had followed Rincewind out of UU), he didn't know what Ankh-Morpork's schooling system was coming to...