[Jedd]

Ask what planet people live on and they'll invariably tell you they live on the Earth.

Whereas in the speculative future, people are unlikely to say they live on the Mars (etc).

[DonHopkins]

Not necessarily. It's not my planet, monkey boy.

Ming the Merciless sidestepped the issue by labeling his buttons in capital letters. [1]

[1] http://3.bp.blogspot.com/-Z9E0myUALKw/UIRPUfNFiBI/AAAAAAAABE...