A feline intruder into my territory.... or a friend?

Dear George,
It’s past midnight and I barely can hold my head up not to fall asleep on the keyboard but I MUST write this letter because I smell trouble in my house. Actually, I’m afraid to go to sleep or better said…..I’m afraid to wake up in the morning. Let me explain. If you remember I was adopted after my human took a trip to Las Vegas. I was extremely happy; I settled in my new home quite nicely; I started an intensive training with my human BUT yesterday I heard him talking about taking a trip to Mexico. You know by now what’s happening when he takes a trip, right? Yes! It possibly means another cat! And now I’m afraid to go to sleep only to wake up in the morning looking at a tabby “Juanita”. I have mixed feelings (due to the recent letters) about sharing the house with another cat. How can I stop my human from going away or better yet, how can I train him to change his habit?
Sleepy but worried,
Vegas

Dear Vegas,
This is one of the worst human habits - their idea that they can just fling another feline into our territory and expect us to accept the intruder. We are not dogs. In nature we would only live with our relatives. Yet they expect us to welcome an unrelated stranger into our midst. Sometimes I despair of humans..... their inability to learn anything about us and their irresponsible habit of adding cats to the household.
You can't stop them, Vegas. You can't change them, Vegas. You can train them out of some behaviour but probably this is a human behaviour problem that won't respond to training. If they bother to read this, they should know that the introduction must be slow, starting with the newcomer in a crate or the spare room (with full litter and food facilities). Bedding should be swapped between you and the new kitten (sounds good that is is female rather than male) so that the proper "family" scent can be developed.
Humans are scent blind and lack our exquisitely sensitive noses. Their honkers or schnozzles are pretty useless organs. It is the scent of the intruder which will initially upset you. However if the scents are slowly mixed and she aquires your scent and visa versa, you may find it in your heart to accept her.
You are young, Vegas. She will be young too. I hope and pray that this willl work out good for you and that, after the initial upset, you will acquire not a competitor but a play mate and a friend. The real pity is that you didn't get the chance to do a joint adoption, you and a littermate adopting the humans together.
Humans... idiots but we love them. Sometimes.
Love George