To fill time while they waited for an appearance on The Jack Paar Program in 1964, Jim Henson, Frank Oz, Don Sahlin and Jerry Juhl decorated some pipes in their dressing room. They left a note that said, "With love, from the Muppets." It was just a spur-of-the-moment prank, and Paar mentioned they would be painted over the next day. But the pipes remained as they were for 46 years. Read the rest of the story at Muppet Wiki. Link -via Metafilter
He got tossed off the air for his W.C. joke.
Back then it was considered risque.
http://www.youtube.com/watch?v=ETzA3fpQp4Y
(it was corny then and it's STILL corny)