One day, a space ship landed in a farmer's field and a Martian man and his
wife got out and introduced themselves to the farmer and his wife. As a
token of his friendship, the farmer immediately invited the Martian couple
in his home and begged them to stay for the evening and have dinner, so the
Martians agreed. Later that night, the Martian man explained how, on their
planet, it was customary to swap partners as a token of friendship. The
farmer, not wanting to offend his alien neighbors, readily agreed.

Then, the Martian man took the farmer's wife in one bedroom while the
farmer took the Martian woman in another bedroom. They had been having
sex for about an hour when the Martian man asked the farmer's wife "Well,
how do you like having sex with a Martian? How does it feel?" The
farmer's wife replied "It needs to be a little bigger around." So the
Martian man twisted his right ear and presto, his penis became bigger
around.

About an hour later, the Martian man asked the farmer's wife again "How
does it feel now?" The farmer's wife responded "I think it needs to be a
little longer." So the Martian man twisted his left ear and presto, his
penis became longer.

The next morning, after their alien neighbors had left, the farmer and his
wife were having coffee at the breakfast table and the farmer asked his wife
"How was the Martian man?" To this, the farmer's wife replied "Fine. And
how about the Martian woman?" The farmer replied "That damn bitch yanked 
on my poor ears all night long!"