Bishop John McGee, secretary to three Popes (Bl Paul VI, John Paul I, and St John Paul II), narrates that just shortly after John Paul I became Pope, he told Msgr McGee, “Would you do me a favor tomorrow morning?”
“Anything you want, Holy Father.”
“Would you celebrate Mass for me?”
“Holy Father, I have been celebrating Mass every day for you.”
“No, I don’t mean that. Would you celebrate Mass and allow me to be your altar server?”
“Holy Father, I couldn’t do that!”
“But it’s the Pope who asks you!”
That’s how Bishop McGee ended up with a Pope as altar server.