(This is based on a story by Bubba1995 that is sadly no longer available. I have attempted to recreate its lore as accurately as possible.)
There is a planet very similar to Earth. However, there is one major difference: there are no men or children over 13. This is the Cougar Planet. As the name implies, the only residents besides children are women aged 30-50, or "cougars". When a child turns 13, they undergo a transformation into a cougar. This may occur during their birthday or a few days, weeks, or sometimes even months later. Some children have a very rare defect that prevents them from changing. These children are sent to live on Earth. If a cougar has sex with a human, they will become infected and turn into a cougar themselves. Cougars reproduce like normal humans; cougars that used to be boys can retract their penis, storing it for safekeeping. Once a cougar has transformed, they may choose which one of their parents will take their virginity. While this is considered abhorrent on Earth, it is considered a normal part of cougar culture.
Cougar Planet is truly a fascinating planet, but who will we be observing this time?