This is one of those jokes you can just save up and unleash at the perfect moment.
The setup is when a female announces that she’s going to ask you a question, but doesn’t actually ask the question.
She: “Hey I need to ask you something”
Then you answer by looking faux defensive, best done by holding your hands in front of you as if to ward her off, but with a knowing little smile and say…
Me: “Oh I’m really flattered, but I’m married“.
As long as she has any level of general attraction for you, and you deliver it with confidence, she’ll love the line. I think it has something to do with both sexualizing the conversation, but also the humor in that you’re trying to sexually defuse it as well. Plus it frames you as the hot one and that she’s the one with the sexual interest. And the preselection mention of a woman you are already having sex with (you wife) and your sexual fidelity as well.
So anyway, I happened to use the line on a cute 23 year old today. Her original intent was to settle an argument with a coworker about whether or not Splenda was made of sugar. She laughed at my line then as I answered her actual question she interestingly snaked her arm around my waist.
Which was a perfect segue into me just smiling and walking away and doing something else.