What should I do about this guy?

So, interesting story. I was on the phone with my fiance and I was reading stuff off her facebook because she doesnt have the internet all the time where she is. And this guy started messaging me on her account. So anyways it progressed and this guy totally was hitting on me, whom he thought was my fiance. Well anyways it has progressed to where he wants to meet up with her. SO there are so many opportunities to scam/doupe/trick/prank/what ever. So my question is what would you guys do if you had this opportunity to totally mess with some guy trying to play your fiance. btw my fiance is aware of this so its not like im snooping or anything. come on fluther use your imagination on this one.