Uncle Diddy is a ghostly relative of Fenwick Quarrel, the deceased great uncle of the sorcerous couple Selwyn and Tallulah, and as a ghost amiably haunts their home Quarrel Castle. His particular specialty is to sing at pitches where he causes things to break. He appeared in the episode "Smurfing For Ghosts", when he along with Fenwick's other relatives are with Fenwick coming to visit him for his Ghost Day.