https://beyondstupidity.blogspot.com/2021/06/the-craziest-murder-alibi-that-someone.html
Good write up on the case. Florida teen goes out with 4 friends, he's the only one to return - alone. When asked what happened, he gives a story about how a 'monster' attacked and killed his friends. After enough people repeatedly pointed out the resemblance to the character, he outright said that the monster he saw was the character (when he was posting to online forums and talking with members). McCleary reportedly suffered a long lasting nervous breakdown until Beany and Cecil had finished airing, in June 1962.
McCleary himself died in 2017. https://www.dignitymemorial.com/obituaries/jacksonville-fl/edward-mccleary-6819524