What's So Bad About Feeling Good?

In this 1968 American fantasy comedy, a misanthropic artist becomes infected with a contagious virus that makes people feel happy, leading to an outbreak of euphoria in New York City's population. As the "victims" spread the virus, the city's economy and social norms begin to collapse, prompting government leaders to approve an urgent vaccination program to turn everyone back to their natural nasty behavior. The film follows Pete's transformation from a cynical artist to a purpose-driven individual who inadvertently destroys the city's economy with his newfound happiness, only for it to be restored when the virus is eventually cured.