Prince
This encounter wasn’t with Prince himself but with Prince’s manager. The OP’s grandfather owned an electronics store back in the day, and he would often rent out concert equipment for local shows. One day the store was really busy, and this guy walks in, passes everyone in line, and goes straight up to the OP’s grandpa at the front desk.
The guy demands help immediately because he’s Prince’s manager; he was probably used to getting special treatment. But the OP’s grandpa had none of it. He calmly explained that this “VIP” manager could get in line and wait like everyone else. When the manager tried to name-drop Prince again, OP’s grandpa was a boss and replied, “I don’t care who Prince is, I’m the king.” Boom.