Since the romantic comedies I write are marketed more toward women than men, I try to sprinkle my stories with predicaments, conversations, and attitudes that tend to amuse the fairer sex. Often, I turn to my personal experiences with the women in my life when pondering ideas for adding humor to my writing. As for age, this is often tougher. It's not easy to find a story line with which women of any age can relate. I tend to concentrate on things more common to younger women.
Chances are, they'll remember.
Too, I strongly believe the best humor derives from a character's response to a situation, rather than simply the situation itself. For example, if that woman being interviewed would've reached up nonchalantly the second she felt the earring slipping and had re-secured it, the situation wouldn't have been nearly as funny. Instead, she froze. This response, and what occurred because of it, generated the humor. Rather than the situation of the body switch sparking the humor, it is sparked by her decision to accept the job with her husband and, later, their interactions with one another as they face his growing attraction to a woman he isn't aware is his own wife.