flash mobbing

an act of organizing a large group of people using social media to gather them together publicly at an exact time, doing something for a short time and then dispersing

Flash mobbing refers to the act of organizing or participating in a flash mob. It involves gathering a group of people, usually through social media or messaging, to perform a planned activity in a public place, such as a dance, song, or other coordinated performance. Flash mobbing is typically done for fun, artistic expression, or to raise awareness for a cause. The participants quickly disperse after the performance, leaving onlookers surprised or entertained.