I’ll go first.
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 once played a wizard who could never learn Fireball, due to having tried to cast it in wizard school before he was ready, and got a facial scar and shock of red in his otherwise black hair.
His go-to eventually became Lightning Bolt, but he was always frustrated by enemies who would never line up to allow him to hit more than two at a time…