This harmonica, and these bells, are sitting in the Smithsonian Museum today. In 1965, however, they were in space, with astronauts Walter M. "Wally" Schirra Jr. and Thomas P. Stafford, who were doing a pre-Christmas mission aboard Gemini 6.

Just before Stafford and Schirra were scheduled to reenter Earth's atmosphere December 16, the pair reported they had sighted some sort of UFO. Schirra recounted the moment when Stafford contacted Mission Control in Schirra's Space, a memoir he wrote with Richard Billings:

"We have an object, looks like a satellite going from north to south, probably in polar orbit…. Looks like he might be going to re-enter soon…. You just might let me pick up that thing…. I see a command module and eight smaller modules in front. The pilot of the command module is wearing a red suit."

Then ground controllers heard the strains, both familiar and otherworldly, of "Jingle Bells." The Santa Claus plot had been hatched weeks before the Gemini 6 mission. "Wally came up with the idea," recalls Stafford, now a retired Air Force general, who chairs an International Space Station advisory group. "He could play the harmonica, and we practiced two or three times before we took off, but of course we didn't tell the guys on the ground."

"I could hear the voices at Mission Control getting tense," Stafford adds, "when I talked about sighting something else up there with us. Then, after we finished the song, [Mission Control's] Elliot See relaxed and just said, 'You're too much.'"