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.
My first long-term DND character was a lore bard who couldn’t play any instruments, who really just wanted to be a wizard. He channelled his music through a kazoo.
Another idea I want to try is a planes walker ranger who got trapped in the feywild and went insane. She always has a story to tell about something that happened to her while she was in the feywild. Some of those stories are true, but most are not.