A person seeks out a fey to get a warlock pact. The person doesn't know, however, that they're a sorcerer with strong fey ancestry that just hasn't manifested yet. The fey obviously agrees to the "pact" and makes a ridiculous contract that the person agrees to. The person lives their entire life believing they're a warlock when they're actually a sorcerer. The only thing the fey did was help the person's magicky shit manifest.
I'm actually very proud if this one. I made a Kenku warlock for a one shot whose background was that he had previously been an actor in a traveling troupe that performed "The Great Wars of the Astral Plane." Being a Kenku, he only spoke in quotes from the play, which he mimicked perfectly.
For the entire night, I only communicated via Star Wars soundboard. It was glorious.
His name? Ujheddye the Fourth. "I am Uhjeddye (a jedi)...like my father before me."