The Batman effect.
A female experimenter, appearing pregnant, boarded the train. In the experimental condition, an additional experimenter dressed as Batman entered from another door. Passengers were significantly more likely to offer their seat when Batman was present (67.21% vs. 37.66%).
[Francesco Pagnini et al.,"Unexpected events and prosocial behavior: the Batman effect", Nature, 2025]
It is a truth universally acknowledged that you should not get to the end of a 1300+ page 5th book in a series and be told there are four more still forthcoming.