Not just for Penises
Wet dreams or 'sleep org*sms' are when you ejaculate or secrete vaginal fluids during your sleep - despite what school sex ed taught us any gender can have them!
Your genitals are super sensitive when you're asleep as there's more blood flow to the area. So if you're having a hot dream, there's a chance you'll orgasm and not know it until you wake up or sometimes you can even wake up mid orgasm!
Grown Ups
You tend to only here about wet dreams when it comes to penis owners going through puberty, but wet dreams can happen at any age.
That being said, they do happen less frequently as you get older, as unlike puberty your hormone levels aren't out of control!
37% of college age vulva-owners in a 1986 study reported to have had at least one orgasm during their sleep.
Dry Dreams
What is more common are, ‘nightime erections’ which I guess you could call ‘Dry Dreams’. This process occurs automatically (spontaneously), without any conscious thought. These can happen at anytime but typically occur during the night as an adult.
It's believed that these serve the purpose of refreshing the erectile tissues with new blood, bringing in fresh oxygen, and clearing away accumulated toxins - keeping it healthy!