I assume you want a magic time-stopper, not one with real-world consequences (like being frozen in unmoving air). But even with magic, the protagonist ages faster than those around them. Let's exploit that:
Gangly 18-year-old genius lad Derek is smitten by 2-years-older Lara who disdains "young boys". Derek builds a magic time-stopper and freezes the outside world for a couple years of his elapsed life -- real-time is only an hour or so. Sure, he takes the opportunity to molest time-frozen women (but no sheep) and steal valuables. When he approaches the babe in his now-matured body, he has piles of cash, gems, etc stashed away. How does she react?
Gender-flipping this could be fun. Under-developed 18-year-old genius gal Shari is smitten by hairy, studly, 2-years-older Thor who disdains stick-figure females. Shari proceeds as above, emerging with more curves and a stash of valuables. Is she still interested in Thor by then?
Twist these. Jac and Josie are nerdy 18-year-old fraternal twins who together build a magic time-stopper. They're not necessarily fixated on any particular individuals, but they synchronously use their device to plunder the world and ravage its frozen inhabitants. Alas, for true love, they have only each other...