Exemplar

Exemplar is a Prestige Class found in Complete Adventurer. Exemplars are all about being really good at specific skills of the player's choice (or DMs choice if NPC). At fifth level they gain the ability to hold demonstrations (assuming it is non-hostile) of their chosen ability in place of Diplomacy checks. With enough levels in Exemplar, you eventually become so good at juggling or bookbinding that you become a magical creature.