Martian sex

A middle aged¹ couple went to a spouse² swapping⁴ party.

They met a Martian couple and thought it would be nice to switch partners for the night.

So they went off with the opposite spouse.

When the woman saw the male martians' penis she said "Well that's nice but it's kind of short isn't it?"

Well the martian reached up and patted his head. While he did that his penis got longer and longer.

The woman saw that and said "That's nice but it's not very fat is it?"

The martian reached up and pulled on his ears. As he was doing that his penis got fatter and fatter.

The women had a grand time that night. In the morning the man and woman were comparing their experience.

The woman said "I really enjoyed myself, we should swap³ again."

The man said "I enjoyed it too but, I just can't figure out why she kept patting my head and pulling my ears!"