I never really laugh out loud while reading but, by golly!

Don't worry, I have not been assaulted or robbed or anything else that would result in a police report. It was the weirdest thing---I was reading in the window seat, and this rather large-bottomed woman boarded the train and made these elaborate preparations to sit down next to me. She pivoted so that she was perpendicular to the seat, backed up very very close to me, and slowly started to lower her ass down. I had time to think, "wait a minute, this chick is going to sit on me" and also to think, "I am being paranoid, people don't just deliberately sit on other people" as the ass descended and then boom, it happened. I made some noise, halfway in between "oof" and "what the fuck?" and sort of pushed at her with my forearms, and she very calmly said, "Oh, I'm terribly sorry" and moved over to the empty seat.

And I sat there angry and bewildered and WHY DID THIS PERSON SIT ON ME. Does a fully-clothed, public-place, sitting on people by "accident" fetish exist? Could a spatial-perception disorder or severe nearsightedness really make someone misjudge a distance that badly? Had I briefly turned invisible?