In 1924, during Mars's opposition (when Earth, on its inner orbit, passes between the Sun and Mars) the US Navy sent a telegram alerting all its stations to be on the lookout for possible alien contact from the red planet. WOW!
Turns out that during the 1924 Mars opposition--when Mars would be closer to Earth than it had been since 1804--the secretary of the Navy sent a telegram to all naval stations asking them to "COOPERATE ASTRONOMERS WHO BELIEVE POSSIBLE THAT MARS MAY ATTEMPT COMMUNICATION BY RADIO WAVES WITH THIS PLANET WHILE THEY ARE NEAR TOGETHER."
BWAHAHAHAHA -- Martians! Like, aliens from Mars! BWAHAHAHAHAHA! I've got news for you: there aren't any aliens on Mars. Pluto, yes, but they're so pissed off we reclassified their home as a dwarf planet they don't have anything to say to us.
UPDATE: I lied, turns out they do have something to say: "F*** you -- have fun with the global warming".
Navy was ordered to listen for Martians in 1924 [scifiwire]
Thanks to junkyard dog, who eats scrap metal and tires and shit because that's what junkyard dogs do.