Ah, OK, I get it. I thought it was like just a work conversation and he was complaining about you to the people he works with.
Well, given the context, I think you need to make some definite rules around that. But "not in a negative light" is pretty amorphous, especially when you're talking about comedy/entertainment. I think it might be a little bit unrealistic to expect him to divine when you'd be OK with it, and when you wouldn't. And it sort of sounds to me like you've tolerated it and this got under your skin particularly because of how your relationship has been.
So I think if you don't want to be the butt of humor, you should tell him that any comments about you are entirely off-limits. Heck, if he makes fun of you after that, you've got a potential invasion of privacy lawsuit. If he doesn't know that, he can ask any entertainment lawyer. By the same token, though, if he chooses to make up a fake girlfriend for the sake of entertainment, I don't think you have any grounds to complain. That's sort of his business, the way I see it.
And yes, he was acting like a jerk. Engaging with him isn't the best strategy. This is where detachment comes in, as in walking away from the conversation.