From the ArcaMax Publishing, Jokes Newsletter:
http://www.arcamax.com/news/jokes/s-569797-567124
An aged farmer and his wife were leaning against the edge of their
pig-pen when the old woman wistfully recalled that the next week would
mark their golden wedding anniversary.
"Let's have a party, Homer," she suggested. "Let's kill a pig."
The farmer scratched his grizzled head.
"Gee, Ethel," he finally answered, "I don't see why the pig should
take the blame for something that happened fifty years ago."