Rincewind
In the first Discworld book, The Colour of Magic, Rincewind was once a student at a magic university. He was very bad at being a wizard. His friends dared him to look in a dangerous forbidden spellbook called The Octavo. When Rincewind looked in the book, one of its eight spells jumped into his head. Because of this,he could never learn any new spells. It also made him forget all the spells he already knew. After this, Rincewind was banished from Unseen University. He started to earn money as a translator. He pretended to be a wizard who became a tour guide for Twoflower, the deuteragonist of the book.