The Apocalypse Starts Right After We Fall in Love

The day after the top and bottom start dating, zombie hordes erupt in multiple places around the world. Roommate One: Holy crap, most people just hurt themselves when they fall in love. You fall in love and you're about to destroy the planet? Roommate Two: From a "scientific" perspective, this can be explained as the "butterfly effect." Roommate Three: Can you break up first and resolve the global crisis? (Looks at them beseechingly.) Top: No way, we're not breaking up! My sweetheart and I aren't taking the blame for this disaster that came out of nowhere! Bottom: ... I just wanted to date someone. What did I ever do to deserve this?