(via Quora) (Answered by John Leavy)
Both humorous and sad.
Alice Cooper says that he was backstage at the Grammies one year chatting with John Lennon. Later on, Brian Wilson of The Beach Boys approached him and said, “That’s John Lennon, isn’t it? Could you introduce us?”
Alice thought, “Wow, I get to introduce two of the all time greats of music.” He introduced them and John cheerfully told Brian what big fans he and Paul McCartney were, and how much The Beach Boys had inspired the the Beatles.
Then, over the next hour, Brian approached Bernie Taupin and a few other people and asked to be introduced to John again and again. Each time, John was gracious and friendly, acting as if he was meeting Brian for the first time ever.
Alice looked at John in confusion. John shrugged, “I’ve known Brian for years. He isn’t well, you know.”