In The End We All Become Stories.

“As Don Corleone calmly explains his idea of “friendship” to the undertaker Bonasera, the first nearly full-body shot of the don reveals an unexpected guest: a gray and white cat sitting in Marlon Brando’s lap. “The cat in Marlon’s hands was not planned for”, director Francis Ford Coppola said later. “I saw the cat running around the studio, and took it and put it in his hands without a word”. Brando apparently loved children and animals, and it became part of the scene. But it also nearly ruined the shot. When the sound crew listened to Brando’s dialogue, they couldn’t understand a word he was saying and feared they would have to use subtitles. The problem wasn’t Brando but the cat, whose purring wrecked the sound. You can still hear it on the sound track.”