What would you do ?

There was I, walking down a pedestrian pathway, children playing, towards a kneehigh closed cardboard box, in the middle of a pedestrian crossroads. Looking at the box till I was right on top of it,then up jumped a child with a loud YAHH from the box. JACKINTHEBOX. I jumped out of my skin,looked around, the children were 'filming' with cellphones, I was laughing for about ten minutes. I don't know any ot them.