"With Love, From the Muppets."
Jim Henson, Frank Oz, Don Sahlin, and Jerry Juhl decorated these steampipes in a dressing room closet at 30 Rockefeller Plaza while killing time before an appearance on The Jack Paar Program in 1964. They've been forgotten about and rediscovered a couple of times through the years, but now they've been preserved and have been made a stop on the NBC Experience tour, thanks in part to Jimmy Fallon. The story on MetaFilter basically quotes from the Muppet wiki, but it links to YouTube clips of the moments mentioned in the article, so check them both out for the full story. (via Tegan)