The objective of the exercise described here is to teach students about group formation using group concepts and theory. It also provides a unique way to form work groups for class projects. Students will become more aware of the reasons people join groups, the benefits groups provide for them, and an understanding of how groups are formed. The exercise takes the class through a fun but educational process of self-selecting into groups. Students begin by choosing things they can relate to, decide if they think similarity or diversity makes for a better group, and unknowingly determine their work groups for class projects through personal choices. Students will be invested in the formation of their own groups, which has the potential for making them more involved throughout the group process. This exercise also serves a practical purpose in that it aids the instructor in forming groups for the class in a somewhat random way. [A list of references and suggested readings is included.]