Cross-dressing FBI chief J. Edgar Hoover apparently wrote a drooling fan letter to Lucille Ball in 1955 to tell her how much he enjoyed the previous Monday's episode of "I Love Lucy," noting "In all the years I have travelled on trains, I have often wondered why someone did not pull the emergency brake, but I have never been aboard a train where it was done. The humor in you program last Monday, I think, exceeded any of your previous programs and they have been really good in themselves."
(Thanks, gruverja!)
Update: Richard sez, "Two years before writing the fan letter, Hoover had opened what became a 50-page spy file on Lucille Ball when a House Committee on Un-American Activities probe revealed she had once registered to vote as a communist. G-Men also put the screws to Ball's husband Desi Arnaz in disapproval of his making a TV show about the FBI busting Ma Barker (allegedly in order to further a rival Warner Bros. hagiography, which Hoover was helping)."