Gretta's land of make believe.

Flatmate and I live in a land of make believe but this land of make believe sometimes completely freaks me out. He says things like he's going to leave his girlfriend and move to my city. I don't believe for 2 seconds he will but then he tries scare tactics and says "Gretta marry me" I play along I don't want him to think he can freak me out. I don't get what he's playing at and to be honest if he was to turn up I don't think I'd quite know what to with him. lol.