In most circumstances, it would be impossible to play baseball with oneself -- or at least a sad sight as you throw the ball, run after it and throw it back the other direction. But, in space, where most sports earthly sports would be considered a challenge, playing baseball by your lonesome is actually achievable.
This Japanese astronaut on the International Space Station filmed himself doing just that here:
According to The Daily Mail, Satoshi Furukawa came up with this activity to amuse himself while on the ISS for a five and a half month stint. Furukawa and two other Japanese astronauts returned safely home from the space station this past Tuesday.