Now it's reversed. Your SO has a clone and the clone is slightly better looking, better body, smarter and funnier. The clone has a very similar personality to your SO, and one day when the two of you are alone, the clone removes its clothes in front of you, and it has a bigger penis/boobs than your SO, and asks that you take its virginity. Do you?
Send in the clones
Yes. That's hot
No. I'm loyal to my SO, and not even a carbon copy of him/her can persuade me
It really depends how drunk I am