Aliens

I'm reading a book called 'The Hitchhiker's Guide to the Galaxy'. There are a lot of aliens in that book. Which is quite obvious because the author is talking about the galaxy. It might not be obvious to a person who doesn't believe in extra terrestrial life, but such a person is fucking stupid. Anyway, the book got me thinking. The aliens in the book are similar to  the organisms on earth because they have the same kind of emotions or feelings that organisms on earth  have.
What if all the 'earthly' feelings are restricted only to life on earth. What if other life forms don't share the same set of feelings that we do. The sex would be weird. Or, there wouldn't be any sex, cause they might not procreate in the same way that we do. Just saying.