When the first Agena Target Vehicle exploded during launch, the Gemini VI mission was left without a rendezvous target. It was soon determined however that the following Gemini VII spacecraft would make a good substitute. Gemini VII with Frank Borman and Jim Lovell aboard launched first. Part of its mission was to spend enough time in space to simulate a journey to the moon and back.
On December 15, 1965 the renamed Gemini VI-A launched crewed by Wally Schirra and Tom Stafford. After achieving orbit the spacecraft was able to locate and maneuver to rendezvous with Gemini VII. The two craft maintained station for 5 hours coming as close as 30 cm. This was the first time two spacecraft had flown so close together in space and confirmed the feasibility of the docking maneuvers that would be required for a journey to the moon.
During the flight, Wally Schirra held up a sign in the window which read “Beat Army” This was a reference to the classic, annual Army/Navy football game. The message intended in jest to Frank Borman in the Gemini VII spacecraft as he was the only one of the four astronauts who was a West Point graduate. The other three being graduates of the Naval Academy. (The game that year between the two service academies was played on Nov. 27, 1965 and ended in a 7-7 tie.)
The sign wasn’t the only surprise Wally had in store on the flight. The next day, before reentry, the crew of Gemini VI-A began transmitting an unexpected message:
“...this is Gemini VI. We have an object, looks like a satellite going from north to south, up in a polar orbit. He's in a very low trajectory traveling from north to south and has a very high climbing ratio. It looks like it might even be a ... Very low. Looks like he might be going to reenter soon. Stand by one ... You might just let me try to pick up that thing.”
At that point, Wally was heard playing "Jingle Bells" on an eight-note Hohner "Little Lady" harmonica which he had brought aboard. A handful of small bells was also heard. At the completion of the song the reply from Mission Control was, “You’re too much Six!”
Of course the object he was referring to was Santa Claus. It is claimed these were the first musical instruments played in space and they are kept on display at the Smithsonian.