Pigs popcorn, fool around, play
Popcorning is a splash of emotions in the animal. To understand the reason for the unusual behavior, remember the events that could make an impression on the pig. It can be treats, a portion of fresh, fragrant hay, an unexpected walk around the apartment, etc.
This phenomenon is contagious. If one animal has already started, then others will join it, but you should not worry — this is a normal phenomenon