As much as people don't mean to hurt anyone's feelings most of the time, this so-called "joke" is/can be somewhat offensive. I know that people like to joke around and what-not, but this can hurt people, even if they know that you were just joking. If you use this as a joke, please be more cautious of how other people feel and only use it as a joke if the other person is fine with it, if the person is not then don't say things like this. I hope you have a nice day/night.
... but, it is hard to pick a gender... istg if another cisgender says "oh, just pick a gender, it's not HARD" i'll slap them I'm not kidding. I'm non binary and that's ok. if any cisgender sees this, I'm warning you to STOP, and if you don't I'll be under your beds tonight pookies