One can tell how close the MAMAMOO members are by seeing how often they touch each others butts.
Wheein is the member that grabs and touches the members the most.
Solar once teased Wheein by shaking her butt in front of her and Wheein had to react.
Hwasa also teased Wheein with her butt by bending over so she sent a message with her fan.
Since Wheein is a serial butt-attacker, Moonbyul stepped in to return the favor.
Moonbyul mustve found it so fun that she decided to do it to Solar too but she kind of backed out in the end.
In the end however, the serial butt-attacker Wheein had to be punished so Hwasa stepped in to deliver the last butt attack.