This is peak physics romance! The stick figure is spinning counterclockwise, claiming it steals angular momentum from Earth, thereby slightly slowing the planet's rotation and extending nighttime. It's a beautifully nerdy way of saying "I want more time with you."
While conservation of angular momentum is a real physical principle, the effect of one person spinning would be so infinitesimally small that you'd need to spin for billions of years to add even a microsecond to the night. But that's what makes this so charming—using ridiculous physics hyperbole as a love declaration.
Classic XKCD—turning fundamental physics into unexpected poetry. Science pickup lines don't get more adorably geeky than this!