I remember reading a book when I was a kid called The Dog Days of Arthur Cane. I think the fairy was a witch doctor but basically the same idea. As I recall, Arthur saw the best and the worst of humanity during his predicament. Sadly no Wikipedia page for the author but the book is on Goodreads: https://www.goodreads.com/book/show/2006378.The_Dog_Days_of_Arthur_Cane