In social psychology, conformity refers to people's tendency to change their behavior due to group pressure, and a Japanese prank show displays this tendency. In the script of the prank, a stranger walking in an empty alley encounters a flood of people running towards him/her. In the show, everyone who faces this situation starts turning around and running, though he/she has no idea what's going on. These strangers are involuntarily involved in the stream because they are under the group pressure. They may think the crowd running towards them is a sign of danger so that they start following others immediately. The reason this prank is successful is that it includes the key factors of conformity. The crowd's action is unanimous: they all run towards the stranger. If a group holds unanimity, a single person in that group is likely to conform. In addition, the size of the group matters. As indicated in the title of the prank show "100 people", the crowd has a large number of people. If the strangers only encounter one or two people, they won't perceive a sense of threat and run away. Hence, this prank show takes advantage of our conformity and illustrates the key factors of the tendency to conform to social pressure.