The Apocalypse Now star plays a married man who leaves his wife for a gay lover in the hit sitcom, and producers wanted to film a skit involving a penis-shaped rodeo bull.

However, Sheen told bosses he was uncomfortable appearing in the same frame as the bizarre object because it was too vulgar for his prudish taste.

He tells Britain's Radio Times magazine, "I'm a prude. I would not participate. Such vulgarity. And I told dear Marta (Kauffman), the writer, it's awful and it's a bad choice.

"I was honest with her, and I'm glad I was. She looked at me and said, 'Well, that's your opinion.' And I said, 'Yes it is, and I'm not participating in that sequence'."