The Met Gala isn’t just about the world’s starriest red carpet. After posing for the cameras, those same stars mingle during the event itself and move on to the string of afterparties that follow.

In fact, fellow musician Katy Perry also addressed an A.I.-generated photo of her attending this year’s Met Gala. “Couldn’t make it to the MET,” she captioned a May 6 Instagram post ...