It's mean to scare people for fun.
John is spending time with his children and family.
John wants to have fun with his son.
John sets up a game for his son to play with him that is fun for both.
John hides from his son only to burst out and take him by suprise.
John's son has a great time and grows a stronger bond with his father.
His son gets frightened and begins to sob uncontrollably ruining the day's fun.