When you pull out of a girl, as you are about to cum, and then discharge your jizz from your wand into her belly button creating a mystical pool of memory and experience, similar to that of Dumbledore's Pensieve.
An allergic reaction that arises upon contact with logic of any kind. This illness is congenital and sometimes passes directly from mother or father to the offspring. To date, it is incurable.
I tried to explain the concept of evolution to my next door neighbor and he replied with an irrelevant Bible quote. I think he may suffer from a form of pensive urticaria.
National pensive day, founded by some discord idiots, is a day where you type in the "pensive" emoji in any social media. The day falls on 6/9, which is the 9th of June.